Theorem List for Metamath Proof Explorer - 27201-27300 *Has distinct variable
group(s)
Type | Label | Description |
Statement |
|
Theorem | 2wspmdisj 27201* |
The sets of paths of length 2 with a given vertex in the middle are
distinct for different vertices in the middle. (Contributed by
Alexander van der Vekens, 11-Mar-2018.) (Revised by AV, 18-May-2021.)
(Proof shortened by AV, 10-Jan-2022.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑀 = (𝑎 ∈ 𝑉 ↦ {𝑤 ∈ (2 WSPathsN 𝐺) ∣ (𝑤‘1) = 𝑎}) ⇒ ⊢ Disj 𝑥 ∈ 𝑉 (𝑀‘𝑥) |
|
Theorem | fusgreghash2wsp 27202* |
In a finite k-regular graph with N vertices there are N times "k choose
2" paths with length 2, according to statement 8 in [Huneke] p. 2: "...
giving n * ( k 2 ) total paths of length two.", if the direction of
traversing the path is not respected. For simple paths of length 2
represented by length 3 strings, however, we have again n*k*(k-1) such
paths. (Contributed by Alexander van der Vekens, 11-Mar-2018.)
(Revised by AV, 19-May-2021.) (Proof shortened by AV, 12-Jan-2022.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝐺 ∈ FinUSGraph ∧ 𝑉 ≠ ∅) → (∀𝑣 ∈ 𝑉 ((VtxDeg‘𝐺)‘𝑣) = 𝐾 → (#‘(2 WSPathsN 𝐺)) = ((#‘𝑉) · (𝐾 · (𝐾 − 1))))) |
|
Theorem | frrusgrord0lem 27203* |
Lemma for frrusgrord0 27204. (Contributed by AV, 12-Jan-2022.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ (((𝐺 ∈ FriendGraph ∧ 𝑉 ∈ Fin ∧ 𝑉 ≠ ∅) ∧ ∀𝑣 ∈ 𝑉 ((VtxDeg‘𝐺)‘𝑣) = 𝐾) → (𝐾 ∈ ℂ ∧ (#‘𝑉) ∈ ℂ ∧
(#‘𝑉) ≠
0)) |
|
Theorem | frrusgrord0 27204* |
If a nonempty finite friendship graph is k-regular, its order is
k(k-1)+1. This corresponds to claim 3 in [Huneke] p. 2: "Next we claim
that the number n of vertices in G is exactly k(k-1)+1.".
(Contributed
by Alexander van der Vekens, 11-Mar-2018.) (Revised by AV,
26-May-2021.) (Proof shortened by AV, 12-Jan-2022.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑉 ∈ Fin ∧ 𝑉 ≠ ∅) → (∀𝑣 ∈ 𝑉 ((VtxDeg‘𝐺)‘𝑣) = 𝐾 → (#‘𝑉) = ((𝐾 · (𝐾 − 1)) + 1))) |
|
Theorem | frrusgrord 27205 |
If a nonempty finite friendship graph is k-regular, its order is
k(k-1)+1. This corresponds to claim 3 in [Huneke] p. 2: "Next we claim
that the number n of vertices in G is exactly k(k-1)+1.". Variant
of
frrusgrord0 27204, using the definition RegUSGraph (df-rusgr 26454).
(Contributed by Alexander van der Vekens, 25-Aug-2018.) (Revised by AV,
26-May-2021.) (Proof shortened by AV, 12-Jan-2022.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝑉 ∈ Fin ∧ 𝑉 ≠ ∅) → ((𝐺 ∈ FriendGraph ∧ 𝐺 RegUSGraph 𝐾) → (#‘𝑉) = ((𝐾 · (𝐾 − 1)) + 1))) |
|
Theorem | numclwlk3lem3 27206 |
Lemma 3 for numclwwlk3 27243. (Contributed by Alexander van der Vekens,
26-Aug-2018.) (Proof shortened by AV, 23-Jan-2022.)
|
⊢ ((𝐾 ∈ ℂ ∧ 𝑌 ∈ ℂ ∧ 𝑁 ∈ (ℤ≥‘2))
→ (((𝐾↑(𝑁 − 2)) − 𝑌) + (𝐾 · 𝑌)) = (((𝐾 − 1) · 𝑌) + (𝐾↑(𝑁 − 2)))) |
|
Theorem | extwwlkfablem1 27207 |
Lemma 1 for extwwlkfab 27223. (Contributed by Alexander van der Vekens,
15-Sep-2018.) (Revised by AV, 27-May-2021.) (Proof shortened by AV,
29-Jan-2022.)
|
⊢ (((𝐺 ∈ USGraph ∧ 𝑁 ∈ (ℤ≥‘2))
∧ 𝑊 ∈ (𝑁 ClWWalksN 𝐺) ∧ (𝑊‘(𝑁 − 2)) = (𝑊‘0)) → (𝑊‘(𝑁 − 1)) ∈ (𝐺 NeighbVtx (𝑊‘0))) |
|
Theorem | clwwlkextfrlem1 27208 |
Lemma for numclwwlk2lem1 27235. (Contributed by Alexander van der Vekens,
3-Oct-2018.) (Revised by AV, 27-May-2021.)
|
⊢ (((𝑁 ∈ ℕ0 ∧ 𝑋 ∈ (Vtx‘𝐺)) ∧ (𝑊 ∈ (𝑁 WWalksN 𝐺) ∧ ( lastS ‘𝑊) ≠ (𝑊‘0))) → (((𝑊 ++ 〈“𝑋”〉)‘0) = (𝑊‘0) ∧ ((𝑊 ++ 〈“𝑋”〉)‘𝑁) ≠ (𝑊‘0))) |
|
Theorem | clwwlksnwwlksn 27209 |
A word representing a closed walk of length 𝑁 also represents a walk
of length 𝑁 − 1. The walk is one edge
shorter than the closed
walk, because the last edge connecting the last with the first vertex is
missing. For example, if 〈“𝑎𝑏𝑐”〉 ∈ (3 ClWWalksN 𝐺)
represents a closed walk "abca" of length 3, then
〈“𝑎𝑏𝑐”〉 ∈ (2 WWalksN 𝐺) represents a walk
"abc" (not closed
if 𝑎 ≠ 𝑐) of length 2, and 〈“𝑎𝑏𝑐𝑎”〉 ∈ (3 WWalksN 𝐺)
represents also a closed walk "abca" of length 3.
(Contributed by AV,
24-Jan-2022.)
|
⊢ ((𝑁 ∈ ℕ ∧ 𝑊 ∈ (𝑁 ClWWalksN 𝐺)) → 𝑊 ∈ ((𝑁 − 1) WWalksN 𝐺)) |
|
Theorem | extwwlkfablem2 27210 |
Lemma 2 for extwwlkfab 27223. (Contributed by Alexander van der Vekens,
15-Sep-2018.) (Revised by AV, 28-May-2021.) (Proof shortened by AV,
24-Jan-2022.)
|
⊢ (((𝐺 ∈ USGraph ∧ 𝑁 ∈ (ℤ≥‘3))
∧ 𝑤 ∈ (𝑁 ClWWalksN 𝐺) ∧ (𝑤‘(𝑁 − 2)) = (𝑤‘0)) → (𝑤 substr 〈0, (𝑁 − 2)〉) ∈ ((𝑁 − 2) ClWWalksN 𝐺)) |
|
Theorem | numclwwlkovf2exlem1 27211 |
Lemma 1 for numclwwlkovf2ex 27219: Transformation of a special
half-open
integer range into a union of a smaller half-open integer range and an
unordered pair. (Contributed by AV, 22-Sep-2018.) (Revised by AV,
26-Jan-2022.)
|
⊢ ((𝑁 ∈ (ℤ≥‘3)
∧ (#‘𝑊) = (𝑁 − 2)) →
(0..^(((#‘𝑊) + 2)
− 1)) = ((0..^((#‘𝑊) − 1)) ∪ {((#‘𝑊) − 1), (#‘𝑊)})) |
|
Theorem | numclwwlkovf2exlem2 27212* |
Lemma 2 for numclwwlkovf2ex 27219: Transformation of a walk and two
edges
into a walk extended by two vertices/edges. (Contributed by AV,
22-Sep-2018.) (Revised by AV, 27-Jan-2022.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐸 = (Edg‘𝐺) ⇒ ⊢ ((((𝐺 ∈ USGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3))
∧ ((𝑊 ∈ Word
𝑉 ∧ ∀𝑖 ∈ (0..^((#‘𝑊) − 1)){(𝑊‘𝑖), (𝑊‘(𝑖 + 1))} ∈ 𝐸 ∧ {( lastS ‘𝑊), (𝑊‘0)} ∈ 𝐸) ∧ (#‘𝑊) = (𝑁 − 2) ∧ (𝑊‘0) = 𝑋)) ∧ 𝑌 ∈ (𝐺 NeighbVtx 𝑋)) → ∀𝑖 ∈ ((0..^((#‘𝑊) − 1)) ∪ {((#‘𝑊) − 1), (#‘𝑊)}){(((𝑊 ++ 〈“𝑋”〉) ++ 〈“𝑌”〉)‘𝑖), (((𝑊 ++ 〈“𝑋”〉) ++ 〈“𝑌”〉)‘(𝑖 + 1))} ∈ 𝐸) |
|
Theorem | numclwwlkovf 27213* |
Value of operation 𝐹, mapping a vertex 𝑣 and a
positive integer
𝑛 to the "(For a fixed vertex v,
let f(n) be the number of) walks
from v to v of length n" according to definition 5 in [Huneke] p. 2.
(Contributed by Alexander van der Vekens, 14-Sep-2018.) (Revised by AV,
28-May-2021.)
|
⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣}) ⇒ ⊢ ((𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → (𝑋𝐹𝑁) = {𝑤 ∈ (𝑁 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑋}) |
|
Theorem | numclwwlkffin 27214* |
In a finite graph, the value of operation 𝐹 is also finite.
(Contributed by Alexander van der Vekens, 26-Sep-2018.) (Revised by AV,
28-May-2021.)
|
⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → (𝑋𝐹𝑁) ∈ Fin) |
|
Theorem | numclwwlkffin0 27215* |
In a finite graph, the value of operation 𝐹 is also finite.
(Contributed by Alexander van der Vekens, 26-Sep-2018.) (Revised by AV,
2-Jun-2021.)
|
⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ0) → (𝑋𝐹𝑁) ∈ Fin) |
|
Theorem | numclwwlkovfel2 27216* |
Properties of an element of the value of operation 𝐹. (Contributed
by Alexander van der Vekens, 20-Sep-2018.) (Revised by AV,
28-May-2021.)
|
⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐸 = (Edg‘𝐺) ⇒ ⊢ ((𝐺 ∈ USGraph ∧ 𝑁 ∈ ℕ ∧ 𝑋 ∈ 𝑉) → (𝑊 ∈ (𝑋𝐹𝑁) ↔ ((𝑊 ∈ Word 𝑉 ∧ ∀𝑖 ∈ (0..^((#‘𝑊) − 1)){(𝑊‘𝑖), (𝑊‘(𝑖 + 1))} ∈ 𝐸 ∧ {( lastS ‘𝑊), (𝑊‘0)} ∈ 𝐸) ∧ (#‘𝑊) = 𝑁 ∧ (𝑊‘0) = 𝑋))) |
|
Theorem | numclwwlkovf2 27217* |
Value of operation 𝐹 for argument 2. (Contributed by
Alexander van
der Vekens, 19-Sep-2018.) (Revised by AV, 28-May-2021.)
|
⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐸 = (Edg‘𝐺) ⇒ ⊢ ((𝐺 ∈ USGraph ∧ 𝑋 ∈ 𝑉) → (𝑋𝐹2) = {𝑤 ∈ Word 𝑉 ∣ ((#‘𝑤) = 2 ∧ {(𝑤‘0), (𝑤‘1)} ∈ 𝐸 ∧ (𝑤‘0) = 𝑋)}) |
|
Theorem | numclwwlkovf2num 27218* |
In a 𝐾-regular graph, there are 𝐾 closed
walks of length 2
starting at a fixed vertex. (Contributed by Alexander van der Vekens,
19-Sep-2018.) (Revised by AV, 28-May-2021.)
|
⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐸 = (Edg‘𝐺) ⇒ ⊢ ((𝐺 RegUSGraph 𝐾 ∧ 𝑋 ∈ 𝑉) → (#‘(𝑋𝐹2)) = 𝐾) |
|
Theorem | numclwwlkovf2ex 27219* |
Extending a closed walk starting at a fixed vertex by an additional edge
(forth and back). (Contributed by AV, 22-Sep-2018.) (Proof shortened
by AV, 25-Jan-2022.)
|
⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐸 = (Edg‘𝐺) ⇒ ⊢ (((𝐺 ∈ USGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3))
∧ 𝑌 ∈ (𝐺 NeighbVtx 𝑋) ∧ 𝑊 ∈ (𝑋𝐹(𝑁 − 2))) → ((𝑊 ++ 〈“𝑋”〉) ++ 〈“𝑌”〉) ∈ (𝑁 ClWWalksN 𝐺)) |
|
Theorem | numclwwlkovg 27220* |
Value of operation 𝐶, mapping a vertex v and an integer n
greater
than 1 to the "closed n-walks v(0) ... v(n-2) v(n-1) v(n) from v =
v(0)
= v(n) with v(n-2) = v" according to definition 6 in [Huneke] p. 2.
(Contributed by Alexander van der Vekens, 14-Sep-2018.) (Revised by AV,
29-May-2021.)
|
⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) ⇒ ⊢ ((𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘2))
→ (𝑋𝐶𝑁) = {𝑤 ∈ (𝑁 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑋 ∧ (𝑤‘(𝑁 − 2)) = (𝑤‘0))}) |
|
Theorem | numclwwlkovgel 27221* |
Properties of an element of the value of operation 𝐶. (Contributed
by Alexander van der Vekens, 24-Sep-2018.) (Revised by AV,
29-May-2021.)
|
⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) ⇒ ⊢ ((𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘2))
→ (𝑊 ∈ (𝑋𝐶𝑁) ↔ (𝑊 ∈ (𝑁 ClWWalksN 𝐺) ∧ (𝑊‘0) = 𝑋 ∧ (𝑊‘(𝑁 − 2)) = (𝑊‘0)))) |
|
Theorem | numclwlk1lem2foalem 27222 |
Lemma for numclwlk1lem2foa 27224. (Contributed by AV, 29-May-2021.)
|
⊢ (((𝑊 ∈ Word 𝑉 ∧ (#‘𝑊) = (𝑁 − 2)) ∧ (𝑋 ∈ 𝑉 ∧ 𝑌 ∈ 𝑉) ∧ 𝑁 ∈ (ℤ≥‘3))
→ ((((𝑊 ++
〈“𝑋”〉) ++ 〈“𝑌”〉) substr 〈0,
(𝑁 − 2)〉) =
𝑊 ∧ (((𝑊 ++ 〈“𝑋”〉) ++
〈“𝑌”〉)‘(𝑁 − 1)) = 𝑌 ∧ (((𝑊 ++ 〈“𝑋”〉) ++ 〈“𝑌”〉)‘(𝑁 − 2)) = 𝑋)) |
|
Theorem | extwwlkfab 27223* |
The set (𝑋𝐶𝑁) of closed walks (having a fixed
length greater
than one and starting at a fixed vertex) with the last but two vertex is
identical with the first (and therefore last) vertex can be constructed
from the set (𝑋𝐹(𝑁 − 2)) of closed walks with
length smaller
by 2 than the fixed length appending a neighbor of the last vertex and
afterwards the last vertex (which is the first vertex) itself
("walking
forth and back" from the last vertex). 3 ≤
𝑁 is required since
for
𝑁 =
2: (𝑋𝐹(𝑁 − 2)) = (𝑋𝐹0) = ∅, see
umgrclwwlksge2 26912 stating that a closed walk of length 0 is
not
represented as word, at least not for an undirected simple graph.
(Contributed by Alexander van der Vekens, 18-Sep-2018.) (Revised by AV,
29-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) ⇒ ⊢ ((𝐺 ∈ USGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3))
→ (𝑋𝐶𝑁) = {𝑤 ∈ (𝑁 ClWWalksN 𝐺) ∣ ((𝑤 substr 〈0, (𝑁 − 2)〉) ∈ (𝑋𝐹(𝑁 − 2)) ∧ (𝑤‘(𝑁 − 1)) ∈ (𝐺 NeighbVtx 𝑋) ∧ (𝑤‘(𝑁 − 2)) = 𝑋)}) |
|
Theorem | numclwlk1lem2foa 27224* |
Going forth and back form the end of a (closed) walk: 𝑊 represents
the closed walk p0, ..., pn-3, p0. With 𝑋 =
p0 and 𝑌 =
pn-1, ((𝑊 ++ 〈“𝑋”〉) ++
〈“𝑌”〉) represents the closed
walk
p0, ..., pn-3, p0, pn-1, p0. (Contributed
by Alexander van der
Vekens, 22-Sep-2018.) (Revised by AV, 29-May-2021.) (Proof shortened
by AV, 30-Jun-2022.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) ⇒ ⊢ ((𝐺 ∈ USGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3))
→ ((𝑊 ∈ (𝑋𝐹(𝑁 − 2)) ∧ 𝑌 ∈ (𝐺 NeighbVtx 𝑋)) → ((𝑊 ++ 〈“𝑋”〉) ++ 〈“𝑌”〉) ∈ (𝑋𝐶𝑁))) |
|
Theorem | numclwlk1lem2f 27225* |
𝑇
is a function, mapping a closed walk having a fixed length and
starting at a fixed vertex) with the last but 2 vertex is identical
with the first (and therefore last) vertex to the pair of the shorter
closed walk and its successor in the longer closed walk, which must be
a neighbor of the first vertex. (Contributed by Alexander van der
Vekens, 19-Sep-2018.) (Revised by AV, 29-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) & ⊢ 𝑇 = (𝑢 ∈ (𝑋𝐶𝑁) ↦ 〈(𝑢 substr 〈0, (𝑁 − 2)〉), (𝑢‘(𝑁 −
1))〉) ⇒ ⊢ ((𝐺 ∈ USGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3))
→ 𝑇:(𝑋𝐶𝑁)⟶((𝑋𝐹(𝑁 − 2)) × (𝐺 NeighbVtx 𝑋))) |
|
Theorem | numclwlk1lem2fv 27226* |
Value of the function 𝑇. (Contributed by Alexander van der
Vekens, 20-Sep-2018.) (Revised by AV, 29-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) & ⊢ 𝑇 = (𝑢 ∈ (𝑋𝐶𝑁) ↦ 〈(𝑢 substr 〈0, (𝑁 − 2)〉), (𝑢‘(𝑁 −
1))〉) ⇒ ⊢ (𝑊 ∈ (𝑋𝐶𝑁) → (𝑇‘𝑊) = 〈(𝑊 substr 〈0, (𝑁 − 2)〉), (𝑊‘(𝑁 − 1))〉) |
|
Theorem | numclwlk1lem2f1 27227* |
𝑇
is a 1-1 function. (Contributed by AV, 26-Sep-2018.) (Revised
by AV, 29-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) & ⊢ 𝑇 = (𝑢 ∈ (𝑋𝐶𝑁) ↦ 〈(𝑢 substr 〈0, (𝑁 − 2)〉), (𝑢‘(𝑁 −
1))〉) ⇒ ⊢ ((𝐺 ∈ USGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3))
→ 𝑇:(𝑋𝐶𝑁)–1-1→((𝑋𝐹(𝑁 − 2)) × (𝐺 NeighbVtx 𝑋))) |
|
Theorem | numclwlk1lem2fo 27228* |
𝑇
is an onto function. (Contributed by Alexander van der Vekens,
20-Sep-2018.) (Revised by AV, 29-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) & ⊢ 𝑇 = (𝑢 ∈ (𝑋𝐶𝑁) ↦ 〈(𝑢 substr 〈0, (𝑁 − 2)〉), (𝑢‘(𝑁 −
1))〉) ⇒ ⊢ ((𝐺 ∈ USGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3))
→ 𝑇:(𝑋𝐶𝑁)–onto→((𝑋𝐹(𝑁 − 2)) × (𝐺 NeighbVtx 𝑋))) |
|
Theorem | numclwlk1lem2f1o 27229* |
𝑇
is a 1-1 onto function. (Contributed by Alexander van der
Vekens, 26-Sep-2018.) (Revised by AV, 29-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) & ⊢ 𝑇 = (𝑢 ∈ (𝑋𝐶𝑁) ↦ 〈(𝑢 substr 〈0, (𝑁 − 2)〉), (𝑢‘(𝑁 −
1))〉) ⇒ ⊢ ((𝐺 ∈ USGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3))
→ 𝑇:(𝑋𝐶𝑁)–1-1-onto→((𝑋𝐹(𝑁 − 2)) × (𝐺 NeighbVtx 𝑋))) |
|
Theorem | numclwlk1lem2 27230* |
There is a bijection between the set of closed walks (having a fixed
length greater than 2 and starting at a fixed vertex) with the last but
2 vertex identical with the first (and therefore last) vertex and the
set of closed walks (having a fixed length less by 2 and starting at the
same vertex) and the neighbors of this vertex. (Contributed by
Alexander van der Vekens, 6-Jul-2018.) (Revised by AV, 29-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) ⇒ ⊢ ((𝐺 ∈ USGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3))
→ ∃𝑓 𝑓:(𝑋𝐶𝑁)–1-1-onto→((𝑋𝐹(𝑁 − 2)) × (𝐺 NeighbVtx 𝑋))) |
|
Theorem | numclwwlk1 27231* |
Statement 9 in [Huneke] p. 2: "If n >
1, then the number of closed
n-walks v(0) ... v(n-2) v(n-1) v(n) from v = v(0) = v(n) with v(n-2) = v
is kf(n-2)". Since 𝐺 is k-regular, the vertex v(n-2) = v
has k
neighbors v(n-1), so there are k walks from v(n-2) = v to v(n) = v (via
each of v's neighbors) completing each of the f(n-2) walks from v=v(0)
to v(n-2)=v. This theorem holds even for k=0, but only for finite
graphs! (Contributed by Alexander van der Vekens, 26-Sep-2018.)
(Revised by AV, 29-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) ⇒ ⊢ (((𝑉 ∈ Fin ∧ 𝐺 RegUSGraph 𝐾) ∧ (𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3)))
→ (#‘(𝑋𝐶𝑁)) = (𝐾 · (#‘(𝑋𝐹(𝑁 − 2))))) |
|
Theorem | numclwwlkovq 27232* |
Value of operation 𝑄, mapping a vertex 𝑣 and a
positive integer
𝑛 to the not closed walks v(0) ... v(n)
of length 𝑛 from a fixed
vertex 𝑣 = v(0). "Not closed" means
v(n) =/= v(0). (Contributed by
Alexander van der Vekens, 27-Sep-2018.) (Revised by AV,
30-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) ⇒ ⊢ ((𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → (𝑋𝑄𝑁) = {𝑤 ∈ (𝑁 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑋 ∧ ( lastS ‘𝑤) ≠ 𝑋)}) |
|
Theorem | numclwwlkqhash 27233* |
In a 𝐾-regular graph, the size of the set
of walks of length 𝑛
starting with a fixed vertex 𝑣 and ending not at this vertex is the
difference between 𝐾 to the power of 𝑛 and the
size of the set
of closed walks of length 𝑛 starting and ending at this vertex
𝑣. (Contributed by Alexander van der
Vekens, 30-Sep-2018.)
(Revised by AV, 30-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) & ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣}) ⇒ ⊢ (((𝐺 RegUSGraph 𝐾 ∧ 𝑉 ∈ Fin) ∧ (𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ)) → (#‘(𝑋𝑄𝑁)) = ((𝐾↑𝑁) − (#‘(𝑋𝐹𝑁)))) |
|
Theorem | numclwwlkovh 27234* |
Value of operation 𝐻, mapping a vertex 𝑣 and a
positive integer
𝑛 to the "closed n-walks v(0) ...
v(n-2) v(n-1) v(n) from v = v(0) =
v(n) ... with v(n-2) =/= v" according to definition 7 in [Huneke] p. 2.
(Contributed by Alexander van der Vekens, 26-Aug-2018.) (Revised by AV,
30-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) & ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) ≠ (𝑤‘0))}) ⇒ ⊢ ((𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → (𝑋𝐻𝑁) = {𝑤 ∈ (𝑁 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑋 ∧ (𝑤‘(𝑁 − 2)) ≠ (𝑤‘0))}) |
|
Theorem | numclwwlk2lem1 27235* |
In a friendship graph, for each walk of length 𝑛 starting at a fixed
vertex 𝑣 and ending not at this vertex, there
is a unique vertex so
that the walk extended by an edge to this vertex and an edge from this
vertex to the first vertex of the walk is a value of operation 𝐻.
If the walk is represented as a word, it is sufficient to add one vertex
to the word to obtain the closed walk contained in the value of
operation 𝐻, since in a word representing a
closed walk the
starting vertex is not repeated at the end. This theorem generally
holds only for Friendship Graphs, because these guarantee that for the
first and last vertex there is a (unique) third vertex "in
between".
(Contributed by Alexander van der Vekens, 3-Oct-2018.) (Revised by AV,
30-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) & ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) ≠ (𝑤‘0))}) ⇒ ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → (𝑊 ∈ (𝑋𝑄𝑁) → ∃!𝑣 ∈ 𝑉 (𝑊 ++ 〈“𝑣”〉) ∈ (𝑋𝐻(𝑁 + 2)))) |
|
Theorem | numclwlk2lem2f 27236* |
𝑅
is a function mapping the "closed (n+2)-walks v(0) ... v(n-2)
v(n-1) v(n) v(n+1) v(n+2) starting at 𝑋 = v(0) = v(n+2) with
v(n)
=/= X" to the words representing the prefix v(0) ... v(n-2)
v(n-1)
v(n) of the walk. (Contributed by Alexander van der Vekens,
5-Oct-2018.) (Revised by AV, 31-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) & ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) ≠ (𝑤‘0))}) & ⊢ 𝑅 = (𝑥 ∈ (𝑋𝐻(𝑁 + 2)) ↦ (𝑥 substr 〈0, (𝑁 + 1)〉))
⇒ ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → 𝑅:(𝑋𝐻(𝑁 + 2))⟶(𝑋𝑄𝑁)) |
|
Theorem | numclwlk2lem2fv 27237* |
Value of the function R. (Contributed by Alexander van der Vekens,
6-Oct-2018.) (Revised by AV, 31-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) & ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) ≠ (𝑤‘0))}) & ⊢ 𝑅 = (𝑥 ∈ (𝑋𝐻(𝑁 + 2)) ↦ (𝑥 substr 〈0, (𝑁 + 1)〉))
⇒ ⊢ ((𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → (𝑊 ∈ (𝑋𝐻(𝑁 + 2)) → (𝑅‘𝑊) = (𝑊 substr 〈0, (𝑁 + 1)〉))) |
|
Theorem | numclwlk2lem2f1o 27238* |
R is a 1-1 onto function. (Contributed by Alexander van der Vekens,
6-Oct-2018.) (Revised by AV, 21-Jan-2022.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) & ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) ≠ (𝑤‘0))}) & ⊢ 𝑅 = (𝑥 ∈ (𝑋𝐻(𝑁 + 2)) ↦ (𝑥 substr 〈0, (𝑁 + 1)〉))
⇒ ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → 𝑅:(𝑋𝐻(𝑁 + 2))–1-1-onto→(𝑋𝑄𝑁)) |
|
Theorem | numclwwlk2lem3 27239* |
In a friendship graph, the size of the set of walks of length 𝑁
starting with a fixed vertex 𝑋 and ending not at this vertex equals
the size of the set of all closed walks of length (𝑁 + 2)
starting
at this vertex 𝑋 and not having this vertex as last
but 2 vertex.
(Contributed by Alexander van der Vekens, 6-Oct-2018.) (Revised by AV,
31-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) & ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) ≠ (𝑤‘0))}) ⇒ ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → (#‘(𝑋𝑄𝑁)) = (#‘(𝑋𝐻(𝑁 + 2)))) |
|
Theorem | numclwwlk2 27240* |
Statement 10 in [Huneke] p. 2: "If n >
1, then the number of closed
n-walks v(0) ... v(n-2) v(n-1) v(n) from v = v(0) = v(n) ... with v(n-2)
=/= v is k^(n-2) - f(n-2)." According to rusgrnumwlkg 26872, we have
k^(n-2) different walks of length (n-2): v(0) ... v(n-2). From this
number, the number of closed walks of length (n-2), which is f(n-2) per
definition, must be subtracted, because for these walks v(n-2) =/= v(0)
= v would hold. Because of the friendship condition, there is exactly
one vertex v(n-1) which is a neighbor of v(n-2) as well as of
v(n)=v=v(0), because v(n-2) and v(n)=v are different, so the number of
walks v(0) ... v(n-2) is identical with the number of walks v(0) ...
v(n), that means each (not closed) walk v(0) ... v(n-2) can be extended
by two edges to a closed walk v(0) ... v(n)=v=v(0) in exactly one way.
(Contributed by Alexander van der Vekens, 6-Oct-2018.) (Revised by AV,
31-May-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) & ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) ≠ (𝑤‘0))}) ⇒ ⊢ (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3)))
→ (#‘(𝑋𝐻𝑁)) = ((𝐾↑(𝑁 − 2)) − (#‘(𝑋𝐹(𝑁 − 2))))) |
|
Theorem | numclwwlk3lem 27241* |
Lemma for numclwwlk3 27243. (Contributed by Alexander van der Vekens,
6-Oct-2018.) (Revised by AV, 1-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) & ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) ≠ (𝑤‘0))}) & ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) ⇒ ⊢ (((𝐺 ∈ FinUSGraph ∧ 𝑋 ∈ 𝑉) ∧ 𝑁 ∈ (ℤ≥‘2))
→ (#‘(𝑋𝐹𝑁)) = ((#‘(𝑋𝐻𝑁)) + (#‘(𝑋𝐶𝑁)))) |
|
Theorem | numclwwlk3OLD 27242* |
Obsolete version of numclwwlk3 27243 as of 21-Jan-2022. (Contributed by
Alexander van der Vekens, 26-Aug-2018.) (Revised by AV, 1-Jun-2021.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 WWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ ( lastS ‘𝑤) ≠ 𝑣)}) & ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣})
& ⊢ 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) ≠ (𝑤‘0))}) & ⊢ 𝐶 = (𝑣 ∈ 𝑉, 𝑛 ∈ (ℤ≥‘2)
↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ ((𝑤‘0) = 𝑣 ∧ (𝑤‘(𝑛 − 2)) = (𝑤‘0))}) ⇒ ⊢ (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3)))
→ (#‘(𝑋𝐹𝑁)) = (((𝐾 − 1) · (#‘(𝑋𝐹(𝑁 − 2)))) + (𝐾↑(𝑁 − 2)))) |
|
Theorem | numclwwlk3 27243* |
Statement 12 in [Huneke] p. 2: "Thus f(n)
= (k - 1)f(n - 2) +
k^(n-2)." - the number of the closed walks v(0) ... v(n-2) v(n-1)
v(n)
is the sum of the number of the closed walks v(0) ... v(n-2) v(n-1)
v(n) with v(n-2) = v(n) (see numclwwlk1 27231) and with v(n-2) =/= v(n)
(see numclwwlk2 27240): f(n) = kf(n-2) + k^(n-2) - f(n-2) =
(k-1)f(n-2) +
k^(n-2). (Contributed by Alexander van der Vekens, 26-Aug-2018.)
(Revised by AV, 21-Jan-2022.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣}) ⇒ ⊢ (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (ℤ≥‘3)))
→ (#‘(𝑋𝐹𝑁)) = (((𝐾 − 1) · (#‘(𝑋𝐹(𝑁 − 2)))) + (𝐾↑(𝑁 − 2)))) |
|
Theorem | numclwwlk4 27244* |
The total number of closed walks in a finite simple graph is the sum of
the numbers of closed walks starting at each of its vertices.
(Contributed by Alexander van der Vekens, 7-Oct-2018.) (Revised by AV,
2-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣}) ⇒ ⊢ ((𝐺 ∈ FinUSGraph ∧ 𝑁 ∈ ℕ) → (#‘(𝑁 ClWWalksN 𝐺)) = Σ𝑥 ∈ 𝑉 (#‘(𝑥𝐹𝑁))) |
|
Theorem | numclwwlk5lem 27245* |
Lemma for numclwwlk5 27246. (Contributed by Alexander van der Vekens,
7-Oct-2018.) (Revised by AV, 2-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣}) ⇒ ⊢ ((𝐺 RegUSGraph 𝐾 ∧ 𝑋 ∈ 𝑉 ∧ 𝐾 ∈ ℕ0) → (2
∥ (𝐾 − 1)
→ ((#‘(𝑋𝐹2)) mod 2) =
1)) |
|
Theorem | numclwwlk5 27246* |
Statement 13 in [Huneke] p. 2: "Let p be
a prime divisor of k-1; then
f(p) = 1 (mod p) [for each vertex v]". (Contributed by Alexander
van
der Vekens, 7-Oct-2018.) (Revised by AV, 2-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺)
& ⊢ 𝐹 = (𝑣 ∈ 𝑉, 𝑛 ∈ ℕ ↦ {𝑤 ∈ (𝑛 ClWWalksN 𝐺) ∣ (𝑤‘0) = 𝑣}) ⇒ ⊢ (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ∧ 𝑉 ∈ Fin) ∧ (𝑋 ∈ 𝑉 ∧ 𝑃 ∈ ℙ ∧ 𝑃 ∥ (𝐾 − 1))) → ((#‘(𝑋𝐹𝑃)) mod 𝑃) = 1) |
|
Theorem | numclwwlk7lem 27247 |
Lemma for numclwwlk7 27249, frgrreggt1 27251 and frgrreg 27252: If a finite,
non-empty friendship graph is 𝐾-regular, the 𝐾 is a nonnegative
integer. (Contributed by AV, 3-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ≠ ∅ ∧ 𝑉 ∈ Fin)) → 𝐾 ∈
ℕ0) |
|
Theorem | numclwwlk6 27248 |
For a prime divisor 𝑃 of 𝐾 − 1, the total
number of closed
walks of length 𝑃 in a 𝐾-regular friendship graph
is equal
modulo 𝑃 to the number of vertices.
(Contributed by Alexander van
der Vekens, 7-Oct-2018.) (Revised by AV, 3-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ∧ 𝑉 ∈ Fin) ∧ (𝑃 ∈ ℙ ∧ 𝑃 ∥ (𝐾 − 1))) → ((#‘(𝑃 ClWWalksN 𝐺)) mod 𝑃) = ((#‘𝑉) mod 𝑃)) |
|
Theorem | numclwwlk7 27249 |
Statement 14 in [Huneke] p. 2: "The total
number of closed walks of
length p [in a friendship graph] is (k(k-1)+1)f(p)=1 (mod p)",
since the
number of vertices in a friendship graph is (k(k-1)+1), see
frrusgrord0 27204 or frrusgrord 27205, and p divides (k-1), i.e. (k-1) mod p =
0 => k(k-1) mod p = 0 => k(k-1)+1 mod p = 1. Since the null graph
is a
friendship graph, see frgr0 27128, as well as k-regular (for any k), see
0vtxrgr 26472, but has no closed walk, see 0clwlk0 26992, this theorem would
be false for a null graph: ((#‘(𝑃 ClWWalksN 𝐺)) mod 𝑃) = 0
≠ 1, so this case must be excluded (by
assuming 𝑉
≠ ∅).
(Contributed by Alexander van der Vekens, 1-Sep-2018.) (Revised by AV,
3-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ≠ ∅ ∧ 𝑉 ∈ Fin) ∧ (𝑃 ∈ ℙ ∧ 𝑃 ∥ (𝐾 − 1))) → ((#‘(𝑃 ClWWalksN 𝐺)) mod 𝑃) = 1) |
|
Theorem | numclwwlk8 27250 |
The size of the set of closed walks of length 𝑃, 𝑃 prime, is
divisible by 𝑃. This corresponds to statement 9 in
[Huneke] p. 2:
"It follows that, if p is a prime number, then the number of closed
walks
of length p is divisible by p", see also clwlksndivn 26972. (Contributed by
Alexander van der Vekens, 7-Oct-2018.) (Revised by AV, 3-Jun-2021.)
|
⊢ ((𝐺 ∈ FinUSGraph ∧ 𝑃 ∈ ℙ) → ((#‘(𝑃 ClWWalksN 𝐺)) mod 𝑃) = 0) |
|
Theorem | frgrreggt1 27251 |
If a finite nonempty friendship graph is 𝐾-regular with 𝐾 > 1,
then 𝐾 must be 2.
(Contributed by Alexander van der Vekens,
7-Oct-2018.) (Revised by AV, 3-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑉 ∈ Fin ∧ 𝑉 ≠ ∅) → ((𝐺 RegUSGraph 𝐾 ∧ 1 < 𝐾) → 𝐾 = 2)) |
|
Theorem | frgrreg 27252 |
If a finite nonempty friendship graph is 𝐾-regular, then 𝐾 must
be 2 (or 0).
(Contributed by Alexander van der Vekens,
9-Oct-2018.) (Revised by AV, 3-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝑉 ∈ Fin ∧ 𝑉 ≠ ∅) → ((𝐺 ∈ FriendGraph ∧ 𝐺 RegUSGraph 𝐾) → (𝐾 = 0 ∨ 𝐾 = 2))) |
|
Theorem | frgrregord013 27253 |
If a finite friendship graph is 𝐾-regular, then it must have order
0, 1 or 3. (Contributed by Alexander van der Vekens, 9-Oct-2018.)
(Revised by AV, 4-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑉 ∈ Fin ∧ 𝐺 RegUSGraph 𝐾) → ((#‘𝑉) = 0 ∨ (#‘𝑉) = 1 ∨ (#‘𝑉) = 3)) |
|
Theorem | frgrregord13 27254 |
If a nonempty finite friendship graph is 𝐾-regular, then it must
have order 1 or 3. Special case of frgrregord013 27253. (Contributed by
Alexander van der Vekens, 9-Oct-2018.) (Revised by AV, 4-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ (((𝐺 ∈ FriendGraph ∧ 𝑉 ∈ Fin ∧ 𝑉 ≠ ∅) ∧ 𝐺 RegUSGraph 𝐾) → ((#‘𝑉) = 1 ∨ (#‘𝑉) = 3)) |
|
Theorem | frgrogt3nreg 27255* |
If a finite friendship graph has an order greater than 3, it cannot be
𝑘-regular for any 𝑘.
(Contributed by Alexander van der Vekens,
9-Oct-2018.) (Revised by AV, 4-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑉 ∈ Fin ∧ 3 < (#‘𝑉)) → ∀𝑘 ∈ ℕ0
¬ 𝐺 RegUSGraph 𝑘) |
|
Theorem | friendshipgt3 27256* |
The friendship theorem for big graphs: In every finite friendship graph
with order greater than 3 there is a vertex which is adjacent to all
other vertices. (Contributed by Alexander van der Vekens, 9-Oct-2018.)
(Revised by AV, 4-Jun-2021.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑉 ∈ Fin ∧ 3 < (#‘𝑉)) → ∃𝑣 ∈ 𝑉 ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ (Edg‘𝐺)) |
|
Theorem | friendship 27257* |
The friendship theorem: In every finite (nonempty) friendship graph
there is a vertex which is adjacent to all other vertices. This is
Metamath 100 proof #83. (Contributed by Alexander van der Vekens,
9-Oct-2018.)
|
⊢ 𝑉 = (Vtx‘𝐺) ⇒ ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑉 ≠ ∅ ∧ 𝑉 ∈ Fin) → ∃𝑣 ∈ 𝑉 ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ (Edg‘𝐺)) |
|
PART 17 GUIDES AND
MISCELLANEA
|
|
17.1 Guides (conventions, explanations, and
examples)
|
|
17.1.1 Conventions
This section describes the conventions we use. These conventions often refer
to existing mathematical practices, which are discussed in more detail in
other references.
For the general conventions, see conventions 27258, and for conventions related
to labels, see conventions-label 27259.
Logic and set theory provide a foundation for all of mathematics. To learn
about them, you should study one or more of the references listed below. We
indicate references using square brackets. The textbooks provide a
motivation for what we are doing, whereas Metamath lets you see in detail all
hidden and implicit steps. Most standard theorems are accompanied by
citations. Some closely followed texts include the following:
- Axioms of propositional calculus - [Margaris].
- Axioms of predicate calculus - [Megill] (System S3' in the article
referenced).
- Theorems of propositional calculus - [WhiteheadRussell].
- Theorems of pure predicate calculus - [Margaris].
- Theorems of equality and substitution - [Monk2], [Tarski], [Megill].
- Axioms of set theory - [BellMachover].
- Development of set theory - [TakeutiZaring]. (The first part of [Quine]
has a good explanation of the powerful device of "virtual" or
class abstractions, which is essential to our development.)
- Construction of real and complex numbers - [Gleason]
- Theorems about real numbers - [Apostol]
|
|
Theorem | conventions 27258 |
Here are some of the conventions we use in the
Metamath Proof Explorer (aka "set.mm"), and how they correspond to
typical textbook language (skipping the many cases
where they are identical).
For conventions related to labels, see conventions-label 27259.
- Notation.
Where possible, the notation attempts to conform to modern
conventions, with variations due to our choice of the axiom system
or to make proofs shorter. However, our notation is strictly
sequential (left-to-right). For example, summation is written in the
form Σ𝑘 ∈ 𝐴𝐵 (df-sum 14417) which denotes that index
variable 𝑘 ranges over 𝐴 when evaluating 𝐵. Thus,
Σ𝑘 ∈ ℕ (1 / (2↑𝑘)) = 1 means 1/2 + 1/4 + 1/8 + ...
= 1 (geoihalfsum 14614).
The notation is usually explained in more detail when first introduced.
- Axiomatic assertions ($a).
All axiomatic assertions ($a statements)
starting with " ⊢ " have labels starting
with "ax-" (axioms) or "df-" (definitions). A statement with a
label starting with "ax-" corresponds to what is traditionally
called an axiom. A statement with a label starting with "df-"
introduces new symbols or a new relationship among symbols
that can be eliminated; they always extend the definition of
a wff or class. Metamath blindly treats $a statements as new
given facts but does not try to justify them. The mmj2 program
will justify the definitions as sound as discussed below,
except for 4 definitions (df-bi 197, df-cleq 2615, df-clel 2618, df-clab 2609)
that require a more complex metalogical justification by hand.
- Proven axioms.
In some cases we wish to treat an expression as an axiom in
later theorems, even though it can be proved. For example,
we derive the postulates or axioms of complex arithmetic as
theorems of ZFC set theory. For convenience, after deriving
the postulates, we reintroduce them as new axioms on
top of set theory. This lets us easily identify which axioms
are needed for a particular complex number proof, without the
obfuscation of the set theory used to derive them. For more, see
mmcomplex.html. When we wish
to use a previously-proven assertion as an axiom, our convention
is that we use the
regular "ax-NAME" label naming convention to define the axiom,
but we precede it with a proof of the same statement with the label
"axNAME" . An example is complex arithmetic axiom ax-1cn 9994,
proven by the preceding theorem ax1cn 9970.
The metamath.exe program will warn if an axiom does not match the
preceding theorem that justifies it if the names match in this way.
- Definitions (df-...).
We encourage definitions to include hypertext links to proven examples.
- Statements with hypotheses. Many theorems and some axioms,
such as ax-mp 5, have hypotheses that must be satisfied in order for
the conclusion to hold, in this case min and maj. When presented in
summarized form such as in the Theorem List (click on "Nearby theorems"
on the ax-mp 5 page), the hypotheses are connected with an ampersand and
separated from the conclusion with a big arrow, such as in " ⊢ 𝜑
& ⊢ (𝜑 → 𝜓) => ⊢ 𝜓". These symbols are _not_
part of the Metamath language but are just informal notation meaning
"and" and "implies".
- Discouraged use and modification.
If something should only be used in limited ways, it is marked with
"(New usage is discouraged.)". This is used, for example, when something
can be constructed in more than one way, and we do not want later
theorems to depend on that specific construction.
This marking is also used if we want later proofs to use proven axioms.
For example, we want later proofs to
use ax-1cn 9994 (not ax1cn 9970) and ax-1ne0 10005 (not ax1ne0 9981), as these
are proven axioms for complex arithmetic. Thus, both
ax1cn 9970 and ax1ne0 9981 are marked as "(New usage is discouraged.)".
In some cases a proof should not normally be changed, e.g., when it
demonstrates some specific technique.
These are marked with "(Proof modification is discouraged.)".
- New definitions infrequent.
Typically, we are minimalist when introducing new definitions; they are
introduced only when a clear advantage becomes apparent for reducing
the number of symbols, shortening proofs, etc. We generally avoid
the introduction of gratuitous definitions because each one requires
associated theorems and additional elimination steps in proofs.
For example, we use < and ≤ for inequality expressions, and
use ((sin‘(i · 𝐴)) / i) instead of (sinh‘𝐴)
for the hyperbolic sine.
- Minimizing axioms and the axiom of choice.
We prefer proofs that depend on fewer and/or weaker axioms,
even if the proofs are longer. In particular, we prefer proofs that do
not use the axiom of choice (df-ac 8939) where such proofs can be found.
The axiom of choice is widely accepted, and ZFC is the most
commonly-accepted fundamental set of axioms for mathematics.
However, there have been and still are some lingering controversies
about the Axiom of Choice. Therefore, where a proof
does not require the axiom of choice, we prefer that proof instead.
E.g., our proof of the Schroeder-Bernstein Theorem (sbth 8080)
does not use the axiom of choice.
In some cases, the weaker axiom of countable choice (ax-cc 9257)
or axiom of dependent choice (ax-dc 9268) can be used instead.
Similarly, any theorem in first order logic (FOL) that
contains only set variables that are all mutually distinct,
and has no wff variables, can be proved *without* using
ax-10 2019 through ax-13 2246, by invoking ax10w 2006 through ax13w 2013.
We encourage proving theorems *without* ax-10 2019 through ax-13 2246
and moving them up to the ax-4 1737 through ax-9 1999 section.
- Alternative (ALT) proofs.
If a different proof is significantly shorter or clearer but
uses more or stronger axioms, we prefer to make that proof an
"alternative" proof (marked with an ALT label suffix), even if
this alternative proof was formalized first.
We then make the proof that requires fewer axioms the main proof.
This has the effect of reducing (over time)
the number and strength of axioms used by any particular proof.
There can be multiple alternatives if it makes sense to do so.
Alternative (*ALT) theorems should have "(Proof modification is
discouraged.) (New usage is discouraged.)" in their comment and should
follow the main statement, so that people reading the text in order will
see the main statement first. The alternative and main statement
comments should use hyperlinks to refer to each other (so that a reader
of one will become easily aware of the other).
- Alternative (ALTV) versions.
If a theorem or definition is an alternative/variant of an already
existing theorem resp. definition, its label should have the same name
with suffix ALTV. Such alternatives should be temporary only, until it
is decided which alternative should be used in the future. Alternative
(*ALTV) theorems or definitions are usually contained in mathboxes.
Their comments need not to contain "(Proof modification is discouraged.)
(New usage is discouraged.)". Alternative statements should follow the
main statement, so that people reading the text in order will see the
main statement first.
- Old (OLD) versions or proofs.
If a proof, definition, axiom, or theorem is going to be removed,
we often stage that change by first renaming its
label with an OLD suffix (to make it clear that it is going to
be removed). Old (*OLD) statements should have "(Proof modification is
discouraged.) (New usage is discouraged.)" and "Obsolete version of
~ xxx as of dd-mmm-yyyy." (not enclosed in parentheses) in the comment.
An old statement should follow the main statement, so that people
reading the text in order will see the main statement first.
This typically happens when a shorter proof to an existing theorem is
found: the existing theorem is kept as an *OLD statement for one year.
When a proof is shortened automatically (using Metamath's minimize_with
command), then it is not necessary to keep the old proof, nor to add
credit for the shortening.
- Variables.
Propositional variables (variables for well-formed formulas or wffs) are
represented with lowercase Greek letters and are normally used
in this order:
𝜑 = phi, 𝜓 = psi, 𝜒 = chi, 𝜃 = theta,
𝜏 = tau, 𝜂 = eta, 𝜁 = zeta, and 𝜎 = sigma.
Individual setvar variables are represented with lowercase Latin letters
and are normally used in this order:
𝑥, 𝑦, 𝑧, 𝑤, 𝑣, 𝑢, and 𝑡.
Variables that represent classes are often represented by
uppercase Latin letters:
𝐴, 𝐵, 𝐶, 𝐷, 𝐸, and so on.
There are other symbols that also represent class variables and suggest
specific purposes, e.g., 0 for poset zero (see p0val 17041) and
connective symbols such as + for some group addition operation.
(See prdsplusgval 16133 for an example of the use of +).
Class variables are selected in alphabetical order starting
from 𝐴 if there is no reason to do otherwise, but many
assertions select different class variables or a different order
to make their intended meaning clearer.
- Turnstile.
"⊢ ", meaning "It is provable that," is the first token
of all assertions
and hypotheses that aren't syntax constructions. This is a standard
convention in logic. For us, it also prevents any ambiguity with
statements that are syntax constructions, such as "wff ¬ 𝜑".
- Biconditional (↔).
There are basically two ways to maximize the effectiveness of
biconditionals (↔):
you can either have one-directional simplifications of all theorems
that produce biconditionals, or you can have one-directional
simplifications of theorems that consume biconditionals.
Some tools (like Lean) follow the first approach, but set.mm follows
the second approach. Practically, this means that in set.mm, for
every theorem that uses an implication in the hypothesis, like
ax-mp 5, there is a corresponding version with a biconditional or a
reversed biconditional, like mpbi 220 or mpbir 221. We prefer this
second approach because the number of duplications in the second
approach is bounded by the size of the propositional calculus section,
which is much smaller than the number of possible theorems in all later
sections that produce biconditionals. So although theorems like
biimpi 206 are available, in most cases there is already a theorem that
combines it with your theorem of choice, like mpbir2an 955, sylbir 225,
or 3imtr4i 281.
- Substitution.
"[𝑦 / 𝑥]𝜑" should be read "the wff that results from the
proper substitution of 𝑦 for 𝑥 in wff 𝜑." See df-sb 1881
and the related df-sbc 3436 and df-csb 3534.
- Is-a-set.
"𝐴 ∈ V" should be read "Class 𝐴 is a set (i.e. exists)."
This is a convention based on Definition 2.9 of [Quine] p. 19.
See df-v 3202 and isset 3207.
However, instead of using 𝐼 ∈ V in the antecedent of a theorem for
some variable 𝐼, we now prefer to use 𝐼 ∈ 𝑉 (or another
variable if 𝑉 is not available) to make it more general. That way we
can often avoid needing extra uses of elex 3212 and syl 17 in the common
case where 𝐼 is already a member of something.
For hypotheses ($e statement) of theorems (mostly in inference form),
however, ⊢ 𝐴 ∈ V is used rather than ⊢ 𝐴 ∈ 𝑉 (e.g.
difexi 4809). This is because 𝐴 ∈ V is almost always satisfied using
an existence theorem stating "... ∈ V", and a hard-coded V in
the $e statement saves a couple of syntax building steps that substitute
V into 𝑉. Notice that this does not hold for hypotheses of
theorems in deduction form: Here still ⊢ (𝜑 → 𝐴 ∈ 𝑉) should be
used rather than ⊢ (𝜑 → 𝐴 ∈ V).
- Converse.
"◡𝑅" should be read "converse of (relation) 𝑅"
and is the same as the more standard notation R^{-1}
(the standard notation is ambiguous). See df-cnv 5122.
This can be used to define a subset, e.g., df-tan 14802 notates
"the set of values whose cosine is a nonzero complex number" as
(◡cos “ (ℂ ∖ {0})).
- Function application.
"(𝐹‘𝑥)" should be read "the value
of function 𝐹 at 𝑥" and has the same meaning as the more
familiar but ambiguous notation F(x). For example,
(cos‘0) = 1 (see cos0 14880). The left apostrophe notation
originated with Peano and was adopted in Definition *30.01 of
[WhiteheadRussell] p. 235, Definition 10.11 of [Quine] p. 68, and
Definition 6.11 of [TakeutiZaring] p. 26. See df-fv 5896.
In the ASCII (input) representation there are spaces around the grave
accent; there is a single accent when it is used directly,
and it is doubled within comments.
- Infix and parentheses.
When a function that takes two classes and produces a class
is applied as part of an infix expression, the expression is always
surrounded by parentheses (see df-ov 6653).
For example, the + in (2 + 2); see 2p2e4 11144.
Function application is itself an example of this.
Similarly, predicate expressions
in infix form that take two or three wffs and produce a wff
are also always surrounded by parentheses, such as
(𝜑 → 𝜓), (𝜑 ∨ 𝜓), (𝜑 ∧ 𝜓), and
(𝜑 ↔ 𝜓)
(see wi 4, df-or 385, df-an 386, and df-bi 197 respectively).
In contrast, a binary relation (which compares two _classes_ and
produces a _wff_) applied in an infix expression is _not_
surrounded by parentheses.
This includes set membership 𝐴 ∈ 𝐵 (see wel 1991),
equality 𝐴 = 𝐵 (see df-cleq 2615),
subset 𝐴 ⊆ 𝐵 (see df-ss 3588), and
less-than 𝐴 < 𝐵 (see df-lt 9949). For the general definition
of a binary relation in the form 𝐴𝑅𝐵, see df-br 4654.
For example, 0 < 1 (see 0lt1 10550) does not use parentheses.
- Unary minus.
The symbol - is used to indicate a unary minus, e.g., -1.
It is specially defined because it is so commonly used.
See cneg 10267.
- Function definition.
Functions are typically defined by first defining the constant symbol
(using $c) and declaring that its symbol is a class with the
label cNAME (e.g., ccos 14795).
The function is then defined labeled df-NAME; definitions
are typically given using the maps-to notation (e.g., df-cos 14801).
Typically, there are other proofs such as its
closure labeled NAMEcl (e.g., coscl 14857), its
function application form labeled NAMEval (e.g., cosval 14853),
and at least one simple value (e.g., cos0 14880).
- Factorial.
The factorial function is traditionally a postfix operation,
but we treat it as a normal function applied in prefix form, e.g.,
(!‘4) = ;24 (df-fac 13061 and fac4 13068).
- Unambiguous symbols.
A given symbol has a single unambiguous meaning in general.
Thus, where the literature might use the same symbol with different
meanings, here we use different (variant) symbols for different
meanings. These variant symbols often have suffixes, subscripts,
or underlines to distinguish them. For example, here
"0" always means the value zero (df-0 9943), while
"0g" is the group identity element (df-0g 16102),
"0." is the poset zero (df-p0 17039),
"0𝑝" is the zero polynomial (df-0p 23437),
"0vec" is the zero vector in a normed subcomplex vector space
(df-0v 27453), and
"0" is a class variable for use as a connective symbol
(this is used, for example, in p0val 17041).
There are other class variables used as connective symbols
where traditional notation would use ambiguous symbols, including
"1", "+", "∗", and "∥".
These symbols are very similar to traditional notation, but because
they are different symbols they eliminate ambiguity.
- ASCII representation of symbols.
We must have an ASCII representation for each symbol.
We generally choose short sequences, ideally digraphs, and generally
choose sequences that vaguely resemble the mathematical symbol.
Here are some of the conventions we use when selecting an
ASCII representation.
We generally do not include parentheses inside a symbol because
that confuses text editors (such as emacs).
Greek letters for wff variables always use the first two letters
of their English names, making them easy to type and easy to remember.
Symbols that almost look like letters, such as ∀,
are often represented by that letter followed by a period.
For example, "A." is used to represent ∀,
"e." is used to represent ∈, and
"E." is used to represent ∃.
Single letters are now always variable names, so constants that are
often shown as single letters are now typically preceded with "_"
in their ASCII representation, for example,
"_i" is the ASCII representation for the imaginary unit i.
A script font constant is often the letter
preceded by "~" meaning "curly", such as "~P" to represent
the power class 𝒫.
Originally, all setvar and class variables used only single letters
a-z and A-Z, respectively. A big change in recent years was to
allow the use of certain symbols as variable names to make formulas
more readable, such as a variable representing an additive group
operation. The convention is to take the original constant token
(in this case "+" which means complex number addition) and put
a period in front of it to result in the ASCII representation of the
variable ".+", shown as +, that can
be used instead of say the letter "P" that had to be used before.
Choosing tokens for more advanced concepts that have no standard
symbols but are represented by words in books, is hard. A few are
reasonably obvious, like "Grp" for group and "Top" for topology,
but often they seem to end up being either too long or too
cryptic. It would be nice if the math community came up with
standardized short abbreviations for English math terminology,
like they have more or less done with symbols, but that probably
won't happen any time soon.
Another informal convention that we've somewhat followed, that is also
not uncommon in the literature, is to start tokens with a
capital letter for collection-like objects and lower case for
function-like objects. For example, we have the collections On
(ordinal numbers), Fin, Prime, Grp, and we have the functions sin,
tan, log, sup. Predicates like Ord and Lim also tend to start
with upper case, but in a sense they are really collection-like,
e.g. Lim indirectly represents the collection of limit ordinals,
but it can't be an actual class since not all limit ordinals
are sets.
This initial capital vs. lower case letter convention is sometimes
ambiguous. In the past there's been a debate about whether
domain and range are collection-like or function-like, thus whether
we should use Dom, Ran or dom, ran. Both are used in the literature.
In the end dom, ran won out for aesthetic reasons
(Norm Megill simply just felt they looked nicer).
- Typography conventions.
Class symbols for functions (e.g., abs, sin)
should usually not have leading or trailing blanks in their
HTML/Latex representation.
This is in contrast to class symbols for operations
(e.g., gcd, sadd, eval), which usually do
include leading and trailing blanks in their representation.
If a class symbol is used for a function as well as an operation
(according to the definition df-ov 6653, each operation value can be
written as function value of an ordered pair), the convention for its
primary usage should be used, e.g. (iEdg‘𝐺) versus
(𝑉iEdg𝐸) for the edges of a graph 𝐺 = 〈𝑉, 𝐸〉.
- Number construction independence.
There are many ways to model complex numbers.
After deriving the complex number postulates we
reintroduce them as new axioms on top of set theory.
This lets us easily identify which axioms are needed
for a particular complex number proof, without the obfuscation
of the set theory used to derive them.
This also lets us be independent of the specific construction,
which we believe is valuable.
See mmcomplex.html for details.
Thus, for example, we don't allow the use of ∅ ∉ ℂ,
as handy as that would be, because that would be
construction-specific. We want proofs about ℂ to be independent
of whether or not ∅ ∈ ℂ.
- Minimize hypotheses
(except for construction independence and number theorem domains).
In most cases we try to minimize hypotheses, that is,
we eliminate or reduce what must be true to prove something, so that
the proof is more general and easier to use.
There are exceptions. For example, we intentionally add hypotheses
if they help make proofs independent of a particular construction
(e.g., the contruction of complex numbers ℂ).
We also intentionally add hypotheses for many real and complex
number theorems to expressly state their domains even when they
are not strictly needed. For example, we could show that
(𝐴 < 𝐵 → 𝐵 ≠ 𝐴) without any other hypotheses, but in
practice we also require proving at least some domains
(e.g., see ltnei 10161). Here are the reasons as discussed in
https://groups.google.com/g/metamath/c/2AW7T3d2YiQ:
- Having the hypotheses immediately shows the intended domain of
applicability (is it ℝ, ℝ*, ω, or something else?),
without having to trace back to definitions.
- Having the hypotheses forces its use in the intended
domain, which generally is desirable.
- The behavior is dependent on accidental behavior of definitions
outside of their domains, so the theorems are non-portable and
"brittle".
- Only a few theorems can have their hypotheses removed
in this fashion due to happy coincidences for our particular
set-theoretical definitions. The poor user (especially a
novice learning real number arithmetic) is going to be
confused not knowing when hypotheses are needed and when
they are not. For someone who hasn't traced back the
set-theoretical foundations of the definitions, it is
seemingly random and isn't intuitive at all.
- The consensus of opinion of people on this group seemed to be
against doing this.
- Natural numbers.
There are different definitions of "natural" numbers in the literature.
We use ℕ (df-nn 11021) for the set of positive integers starting
from 1, and ℕ0 (df-n0 11293) for the set of nonnegative integers
starting at zero.
- Decimal numbers.
Numbers larger than nine are often expressed in base 10 using the
decimal constructor df-dec 11494, e.g., ;;;4001 (see 4001prm 15852
for a proof that 4001 is prime).
- Theorem forms.
We will use the following descriptive terms to categorize theorems:
- A theorem is in "closed form" if it has no $e hypotheses
(e.g., unss 3787). The term "tautology" is also used, especially in
propositional calculus. This form was formerly called "theorem form"
or "closed theorem form".
- A theorem is in "deduction form" (or is a "deduction") if it
has zero or more $e hypotheses, and the hypotheses and the conclusion
are implications that share the same antecedent. More precisely, the
conclusion is an implication with a wff variable as the antecedent
(usually 𝜑), and every hypothesis ($e statement) is either:
- an implication with the same antecedent as the conclusion, or
- a definition. A definition can be for a class variable (this is a
class variable followed by =, e.g. the definition of 𝐷 in
lhop 23779) or a wff variable (this is a wff variable followed by
↔); class variable definitions are more common.
In practice, a proof of a theorem in deduction form will also contain
many steps that are implications where the antecedent is either that
wff variable (usually 𝜑) or is a conjunction (𝜑 ∩ ...)
including that wff variable (𝜑). E.g. a1d 25, unssd 3789.
Although they are no real deductions, theorems without $e hypotheses,
but in the form (𝜑 → ...), are also said to be in "deduction
form". Such theorems usually have a two step proof, applying a1i 11 to a
given theorem, and are used as convenience theorems to shorten many
proofs. E.g. eqidd 2623, which is used more than 1500 times.
- A theorem is in "inference form" (or is an "inference") if
it has one or more $e hypotheses, but is not in deduction form,
i.e. there is no common antecedent (e.g., unssi 3788).
Any theorem whose conclusion is an implication has an associated
inference, whose hypotheses are the hypotheses of that theorem
together with the antecedent of its conclusion, and whose conclusion is
the consequent of that conclusion. When both theorems are in set.mm,
then the associated inference is often labeled by adding the suffix "i"
to the label of the original theorem (for instance, con3i 150 is the
inference associated with con3 149). The inference associated with a
theorem is easily derivable from that theorem by a simple use of
ax-mp 5. The other direction is the subject of the Deduction Theorem
discussed below. We may also use the term "associated inference" when
the above process is iterated. For instance, syl 17 is an
inference associated with imim1 83 because it is the inference
associated with imim1i 63 which is itself the inference
associated with imim1 83.
"Deduction form" is the preferred form for theorems because this form
allows us to easily use the theorem in places where (in traditional
textbook formalizations) the standard Deduction Theorem (see below)
would be used. We call this approach "deduction style".
In contrast, we usually avoid theorems in "inference form" when that
would end up requiring us to use the deduction theorem.
Deductions have a label suffix of "d", especially if there are other
forms of the same theorem (e.g., pm2.43d 53). The labels for inferences
usually have the suffix "i" (e.g., pm2.43i 52). The labels of theorems
in "closed form" would have no special suffix (e.g., pm2.43 56). When
an inference is converted to a theorem by eliminating an "is a set"
hypothesis, we sometimes suffix the closed form with "g" (for "more
general") as in uniex 6953 vs. uniexg 6955.
- Deduction theorem.
The Deduction Theorem is a metalogical theorem that provides an
algorithm for constructing a proof of a theorem from the proof of its
corresponding deduction (its associated inference). See for instance
Theorem 3 in [Margaris] p. 56. In ordinary mathematics, no one actually
carries out the algorithm, because (in its most basic form) it involves
an exponential explosion of the number of proof steps as more hypotheses
are eliminated. Instead, in ordinary mathematics the Deduction Theorem
is invoked simply to claim that something can be done in principle,
without actually doing it. For more details, see mmdeduction.html.
The Deduction Theorem is a metalogical theorem that cannot be applied
directly in metamath, and the explosion of steps would be a problem
anyway, so alternatives are used. One alternative we use sometimes is
the "weak deduction theorem" dedth 4139, which works in certain cases in
set theory. We also sometimes use dedhb 3376. However, the primary
mechanism we use today for emulating the deduction theorem is to write
proofs in deduction form (aka "deduction style") as described earlier;
the prefixed 𝜑 → mimics the context in a deduction proof system.
In practice this mechanism works very well. This approach is described
in the deduction form and natural deduction page mmnatded.html; a
list of translations for common natural deduction rules is given in
natded 27260.
- Recursion.
We define recursive functions using various "recursion constructors".
These allow us to define, with compact direct definitions, functions
that are usually defined in textbooks with indirect self-referencing
recursive definitions. This produces compact definition and much
simpler proofs, and greatly reduces the risk of creating unsound
definitions. Examples of recursion constructors include
recs(𝐹) in df-recs 7468, rec(𝐹, 𝐼) in df-rdg 7506,
seq𝜔(𝐹, 𝐼) in df-seqom 7543, and seq𝑀( + , 𝐹) in
df-seq 12802. These have characteristic function 𝐹 and initial value
𝐼. (Σg in df-gsum 16103 isn't really designed for arbitrary
recursion, but you could do it with the right magma.) The logically
primary one is df-recs 7468, but for the "average user" the most useful
one is probably df-seq 12802- provided that a countable sequence is
sufficient for the recursion.
- Extensible structures.
Mathematics includes many structures such as ring, group, poset, etc.
We define an "extensible structure" which is then used to define group,
ring, poset, etc. This allows theorems from more general structures
(groups) to be reused for more specialized structures (rings) without
having to reprove them. See df-struct 15859.
- Undefined results and "junk theorems".
Some expressions are only expected to be meaningful in certain contexts.
For example, consider Russell's definition description binder iota,
where (℩𝑥𝜑) is meant to be "the 𝑥 such that 𝜑"
(where 𝜑 typically depends on x).
What should that expression produce when there is no such 𝑥?
In set.mm we primarily use one of two approaches.
One approach is to make the expression evaluate to the empty set
whenever the expression is being used outside of its expected context.
While not perfect, it makes it a bit more clear when something
is undefined, and it has the advantage that it makes more
things equal outside their domain which can remove hypotheses when
you feel like exploiting these so-called junk theorems.
Note that Quine does this with iota (his definition of iota
evaluates to the empty set when there is no unique value of 𝑥).
Quine has no problem with that and we don't see why we should,
so we define iota exactly the same way that Quine does.
The main place where you see this being systematically exploited is in
"reverse closure" theorems like 𝐴 ∈ (𝐹‘𝐵) → 𝐵 ∈ dom 𝐹,
which is useful when 𝐹 is a family of sets. (by this we
mean it's a set set even in a type theoretic interpretation.)
The second approach uses "(New usage is discouraged.)" to prevent
unintentional uses of certain properties.
For example, you could define some construct df-NAME whose
usage is discouraged, and prove only the specific properties
you wish to use (and add those proofs to the list of permitted uses
of "discouraged" information). From then on, you can only use
those specific properties without a warning.
Other approaches often have hidden problems.
For example, you could try to "not define undefined terms"
by creating definitions like ${ $d 𝑦𝑥 $. $d 𝑦𝜑 $.
df-iota $a ⊢ (∃!𝑥𝜑 → (℩𝑥𝜑) = ∪ {𝑥 ∣ 𝜑}) $. $}.
This will be rejected by the definition checker, but the bigger
theoretical reason to reject this axiom is that it breaks equality -
the metatheorem (𝑥 = 𝑦 → P(x) = P(y) ) fails
to hold if definitions don't unfold without some assumptions.
(That is, iotabidv 5872 is no longer provable and must be added
as an axiom.) It is important for every syntax constructor to
satisfy equality theorems *unconditionally*, e.g., expressions
like (1 / 0) = (1 / 0) should not be rejected.
This is forced on us by the context free term
language, and anything else requires a lot more infrastructure
(e.g., a type checker) to support without making everything else
more painful to use.
Another approach would be to try to make nonsensical
statements syntactically invalid, but that can create its own
complexities; in some cases that would make parsing itself undecidable.
In practice this does not seem to be a serious issue.
No one does these things deliberately in "real" situations,
and some knowledgeable people (such as Mario Carneiro)
have never seen this happen accidentally.
Norman Megill doesn't agree that these "junk" consequences are
necessarily bad anyway, and they can significantly shorten proofs
in some cases. This database would be much larger if, for example,
we had to condition fvex 6201 on the argument being in the domain
of the function. It is impossible to derive a contradiction
from sound definitions (i.e. that pass the definition check),
assuming ZFC is consistent, and he doesn't see the point of all the
extra busy work and huge increase in set.mm size that would result
from restricting *all* definitions.
So instead of implementing a complex system to counter a
problem that does not appear to occur in practice, we use
a significantly simpler set of approaches.
- Organizing proofs.
Humans have trouble understanding long proofs.
It is often preferable to break longer proofs into
smaller parts (just as with traditional proofs). In Metamath
this is done by creating separate proofs of the separate parts.
A proof with the sole purpose of supporting a final proof is a
lemma; the naming convention for a lemma is the final proof's name
followed by "lem", and a number if there is more than one. E.g.,
sbthlem1 8070 is the first lemma for sbth 8080. Also, consider proving
reusable results separately, so that others will be able to easily
reuse that part of your work.
- Limit proof size.
It is often preferable to break longer proofs into
smaller parts, just as you would do with traditional proofs.
One reason is that humans have trouble understanding long proofs.
Another reason is that it's generally best to prove
reusable results separately,
so that others will be able to easily reuse them.
Finally, the "minimize" routine can take much longer with
very long proofs.
We encourage proofs to be no more than 200 essential steps, and
generally no more than 500 essential steps,
though these are simply guidelines and not hard-and-fast rules.
Much smaller proofs are fine!
We also acknowledge that some proofs, especially autogenerated ones,
should sometimes not be broken up (e.g., because
breaking them up might be useless and inefficient due to many
interconnections and reused terms within the proof).
In Metamath, breaking up longer proofs is done by creating multiple
separate proofs of separate parts.
A proof with the sole purpose of supporting a final proof is a
lemma; the naming convention for a lemma is the final proof's name
followed by "lem", and a number if there is more than one. E.g.,
sbthlem1 8070 is the first lemma for sbth 8080.
- Hypertext links.
We strongly encourage comments to have many links to related material,
with accompanying text that explains the relationship. These can help
readers understand the context. Links to other statements, or to
HTTP/HTTPS URLs, can be inserted in ASCII source text by prepending a
space-separated tilde (e.g., " ~ df-prm " results in " df-prm 15386").
When metamath.exe is used to generate HTML it automatically inserts
hypertext links for syntax used (e.g., every symbol used), every axiom
and definition depended on, the justification for each step in a proof,
and to both the next and previous assertion.
- Hypertext links to section headers.
Some section headers have text under them that describes or explains the
section. However, they are not part of the description of axioms or
theorems, and there is no way to link to them directly. To provide for
this, section headers with accompanying text (indicated with "*"
prefixed to mmtheorems.html#mmdtoc entries) have an anchor in
mmtheorems.html whose name is the first $a or $p statement that
follows the header. For example there is a glossary under the section
heading called GRAPH THEORY. The first $a or $p statement that follows
is cedgf 25867. To reference it we link to the anchor using a
space-separated tilde followed by the space-separated link
mmtheorems.html#cedgf, which will become the hyperlink
mmtheorems.html#cedgf. Note that no theorem in set.mm is allowed to
begin with "mm" (enforced by "verify markup" in the metamath program).
Whenever the software sees a tilde reference beginning with "http:",
"https:", or "mm", the reference is assumed to be a link to something
other than a statement label, and the tilde reference is used as is.
This can also be useful for relative links to other pages such as
mmcomplex.html.
- Bibliography references.
Please include a bibliographic reference to any external material used.
A name in square brackets in a comment indicates a
bibliographic reference. The full reference must be of the form
KEYWORD IDENTIFIER? NOISEWORD(S)* [AUTHOR(S)] p. NUMBER -
note that this is a very specific form that requires a page number.
There should be no comma between the author reference and the
"p." (a constant indicator).
Whitespace, comma, period, or semicolon should follow NUMBER.
An example is Theorem 3.1 of [Monk1] p. 22,
The KEYWORD, which is not case-sensitive,
must be one of the following: Axiom, Chapter, Compare, Condition,
Corollary, Definition, Equation, Example, Exercise, Figure, Item,
Lemma, Lemmas, Line, Lines, Notation, Part, Postulate, Problem,
Property, Proposition, Remark, Rule, Scheme, Section, or Theorem.
The IDENTIFIER is optional, as in for example
"Remark in [Monk1] p. 22".
The NOISEWORDS(S) are zero or more from the list: from, in, of, on.
The AUTHOR(S) must be present in the file identified with the
htmlbibliography assignment (e.g., mmset.html) as a named anchor
(NAME=). If there is more than one document by the same author(s),
add a numeric suffix (as shown here).
The NUMBER is a page number, and may be any alphanumeric string such as
an integer or Roman numeral.
Note that we _require_ page numbers in comments for individual
$a or $p statements. We allow names in square brackets without
page numbers (a reference to an entire document) in
heading comments.
If this is a new reference, please also add it to the
"Bibliography" section of mmset.html.
(The file mmbiblio.html is automatically rebuilt, e.g.,
using the metamath.exe "write bibliography" command.)
- Acceptable shorter proofs
Shorter proofs are welcome, and any shorter proof we accept
will be acknowledged in the theorem's description. However,
in some cases a proof may be "shorter" or not depending on
how it is formatted. This section provides general guidelines.
Usually we automatically accept shorter proofs that (1)
shorten the set.mm file (with compressed proofs), (2) reduce
the size of the HTML file generated with SHOW STATEMENT xx
/ HTML, (3) use only existing, unmodified theorems in the
database (the order of theorems may be changed, though), and
(4) use no additional axioms.
Usually we will also automatically accept a _new_ theorem
that is used to shorten multiple proofs, if the total size
of set.mm (including the comment of the new theorem, not
including the acknowledgment) decreases as a result.
In borderline cases, we typically place more importance on
the number of compressed proof steps and less on the length
of the label section (since the names are in principle
arbitrary). If two proofs have the same number of compressed
proof steps, we will typically give preference to the one
with the smaller number of different labels, or if these
numbers are the same, the proof with the fewest number of
characters that the proofs happen to have by chance when
label lengths are included.
A few theorems have a longer proof than necessary in order
to avoid the use of certain axioms, for pedagogical purposes,
and for other reasons. These theorems will (or should) have
a "(Proof modification is discouraged.)" tag in their
description. For example, idALT 23 shows a proof directly from
axioms. Shorter proofs for such cases won't be accepted,
of course, unless the criteria described continues to be
satisfied.
- Input format.
The input is in ASCII with two-space indents. Tab characters are not
allowed. Use embedded math comments or HTML entities for non-ASCII
characters (e.g., "é" for "é").
- Information on syntax, axioms, and definitions.
For a hyperlinked list of syntax, axioms, and definitions, see
mmdefinitions.html.
If you have questions about a specific symbol or axiom, it is best
to go directly to its definition to learn more about it.
The generated HTML for each theorem and axiom includes hypertext
links to each symbol's definition.
- Reserved symbols: 'LETTER.
Some symbols are reserved for potential future use.
Symbols with the pattern 'LETTER are reserved for possibly
representing characters (this is somewhat similar to Lisp).
We would expect '\n to represent newline, 'sp for space, and perhaps
'\x24 for the dollar character.
- Language and spelling.
It is preferred to use American English for comments and symbols, e.g.
we use "neighborhood" instead of the British English "neighbourhood".
An exception is the word "analog", which can be either a noun or an
adjective. Furthermore, "analog" has the confounding meaning "not
digital", whereas "analogue" is often used in the sense something that
bears analogy to something else also in American English. Therefore,
"analogue" is used for the noun and "analogous" for the adjective in
set.mm.
- Comments and layout.
As for formatting of the file set.mm, and in particular formatting and
layout of the comments, the foremost rule is consistency. The first
sections of set.mm, in particular Part 1 "Classical first-order logic
with equality" can serve as a model for contributors. Some formatting
rules are enforced when using the Metamath program's "WRITE SOURCE"
command with the "REWRAP" option. Here are a few other rules, which are
not enforced, but that we try follow:
-
The file set.mm should have a double blank line before each section
header, and at no other places. In particular, there are no triple
blank lines. If there is a "@( Begin $[ ... $] @)" comment (where "@"
is actually "$") before the section header, then the double blank line
should go before that comment.
-
The header comments should be spaced as those of Part 1, namely, with
a blank line before and after the comment, and an indentation of two
spaces.
-
Header comments are not rewrapped by the Metamath program [as of
24-Oct-2021], but similar spacing and wrapping should be used as for
other comments: double spaces after a period ending a sentence, line
wrapping with line width of 79, and no trailing spaces at the end of
lines.
The challenge of varying mathematical conventions
We try to follow mathematical conventions, but in many cases
different texts use different conventions.
In those cases we pick some reasonably common convention and stick to
it.
We have already mentioned that the term "natural number" has
varying definitions (some start from 0, others start from 1), but
that is not the only such case.
A useful example is the set of metavariables used to represent
arbitrary well-formed formulas (wffs).
We use an open phi, φ, to represent the first arbitrary wff in an
assertion with one or more wffs; this is a common convention and
this symbol is easily distinguished from the empty set symbol.
That said, it is impossible to please everyone or simply "follow
the literature" because there are many different conventions for
a variable that represents any arbitrary wff.
To demonstrate the point,
here are some conventions for variables that represent an arbitrary
wff and some texts that use each convention:
- open phi φ (and so on): Tarski's papers,
Rasiowa & Sikorski's
The Mathematics of Metamathematics (1963),
Monk's Introduction to Set Theory (1969),
Enderton's Elements of Set Theory (1977),
Bell & Machover's A Course in Mathematical Logic (1977),
Jech's Set Theory (1978),
Takeuti & Zaring's
Introduction to Axiomatic Set Theory (1982).
- closed phi ϕ (and so on):
Levy's Basic Set Theory (1979),
Kunen's Set Theory (1980),
Paulson's Isabelle: A Generic Theorem Prover (1994),
Huth and Ryan's Logic in Computer Science (2004/2006).
- Greek α, β, γ:
Duffy's Principles of Automated Theorem Proving (1991).
- Roman A, B, C:
Kleene's Introduction to Metamathematics (1974),
Smullyan's First-Order Logic (1968/1995).
- script A, B, C:
Hamilton's Logic for Mathematicians (1988).
- italic A, B, C:
Mendelson's Introduction to Mathematical Logic (1997).
- italic P, Q, R:
Suppes's Axiomatic Set Theory (1972),
Gries and Schneider's A Logical Approach to Discrete Math
(1993/1994),
Rosser's Logic for Mathematicians (2008).
- italic p, q, r:
Quine's Set Theory and Its Logic (1969),
Kuratowski & Mostowski's Set Theory (1976).
- italic X, Y, Z:
Dijkstra and Scholten's
Predicate Calculus and Program Semantics (1990).
- Fraktur letters:
Fraenkel et. al's Foundations of Set Theory (1973).
Distinctness or freeness
Here are some conventions that address distinctness or freeness of a
variable:
- Ⅎ𝑥𝜑 is read " 𝑥 is not free in (wff) 𝜑";
see df-nf 1710 (whose description has some important technical
details). Similarly, Ⅎ𝑥𝐴 is read 𝑥 is not free in (class)
𝐴, see df-nfc 2753.
- "$d x y $." should be read "Assume x and y are distinct
variables."
- "$d x 𝜑 $." should be read "Assume x does not occur in phi $."
Sometimes a theorem is proved using
Ⅎ𝑥𝜑 (df-nf 1710) in place of
"$d 𝑥𝜑 $." when a more general result is desired;
ax-5 1839 can be used to derive the $d version. For an example of
how to get from the $d version back to the $e version, see the
proof of euf 2478 from df-eu 2474.
- "$d x A $." should be read "Assume x is not a variable occurring in
class A."
- "$d x A $. $d x ps $. $e |- (𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) $."
is an idiom
often used instead of explicit substitution, meaning "Assume psi results
from the proper substitution of A for x in phi."
- " ⊢ (¬ ∀𝑥𝑥 = 𝑦 → ..." occurs early in some cases, and
should be read "If x and y are distinct
variables, then..." This antecedent provides us with a technical
device (called a "distinctor" in Section 7 of [Megill] p. 444)
to avoid the need for the
$d statement early in our development of predicate calculus, permitting
unrestricted substitutions as conceptually simple as those in
propositional calculus. However, the $d eventually becomes a
requirement, and after that this device is rarely used.
There is a general technique to replace a $d x A or
$d x ph condition in a theorem with the corresponding
Ⅎ𝑥𝐴 or Ⅎ𝑥𝜑; here it is.
⊢ T[x, A] where $d 𝑥𝐴,
and you wish to prove ⊢ Ⅎ𝑥𝐴 ⇒ ⊢ T[x, A].
You apply the theorem substituting 𝑦 for 𝑥 and 𝐴 for 𝐴,
where 𝑦 is a new dummy variable, so that
$d y A is satisfied.
You obtain ⊢ T[y, A], and apply chvar to obtain ⊢
T[x, A] (or just use mpbir 221 if T[x, A] binds 𝑥).
The side goal is ⊢ (𝑥 = 𝑦 → ( T[y, A] ↔ T[x, A] )),
where you can use equality theorems, except
that when you get to a bound variable you use a non-dv bound variable
renamer theorem like cbval 2271. The section
mmtheorems32.html#mm3146s also describes the
metatheorem that underlies this.
Standard Metamath verifiers do not distinguish between axioms and
definitions (both are $a statements).
In practice, we require that definitions (1) be conservative
(a definition should not allow an expression
that previously qualified as a wff but was not provable
to become provable) and be eliminable
(there should exist an algorithmic method for converting any
expression using the definition into
a logically equivalent expression that previously qualified as a wff).
To ensure this, we have additional rules on almost all definitions
($a statements with a label that does not begin with ax-).
These additional rules are not applied in a few cases where they
are too strict (df-bi 197, df-clab 2609, df-cleq 2615, and df-clel 2618);
see those definitions for more information.
These additional rules for definitions are checked by at least
mmj2's definition check (see
mmj2 master file mmj2jar/macros/definitionCheck.js).
This definition check relies on the database being very much like
set.mm, down to the names of certain constants and types, so it
cannot apply to all Metamath databases... but it is useful in set.mm.
In this definition check, a $a-statement with a given label and
typecode ⊢ passes the test if and only if it
respects the following rules (these rules require that we have
an unambiguous tree parse, which is checked separately):
- The expression must be a biconditional or an equality (i.e. its
root-symbol must be ↔ or =).
If the proposed definition passes this first rule, we then
define its definiendum as its left hand side (LHS) and
its definiens as its right hand side (RHS).
We define the *defined symbol* as the root-symbol of the LHS.
We define a *dummy variable* as a variable occurring
in the RHS but not in the LHS.
Note that the "root-symbol" is the root of the considered tree;
it need not correspond to a single token in the database
(e.g., see w3o 1036 or wsb 1880).
- The defined expression must not appear in any statement
between its syntax axiom ($a wff ) and its definition,
and the defined expression must not be used in its definiens.
See df-3an 1039 for an example where the same symbol is used in
different ways (this is allowed).
- No two variables occurring in the LHS may share a
disjoint variable (DV) condition.
- All dummy variables are required to be disjoint from any
other (dummy or not) variable occurring in this labeled expression.
- Either
(a) there must be no non-setvar dummy variables, or
(b) there must be a justification theorem.
The justification theorem must be of form
⊢ ( definiens root-symbol definiens' )
where definiens' is definiens but the dummy variables are all
replaced with other unused dummy variables of the same type.
Note that root-symbol is ↔ or =, and that setvar
variables are simply variables with the setvar typecode.
- One of the following must be true:
(a) there must be no setvar dummy variables,
(b) there must be a justification theorem as described in rule 5, or
(c) if there are setvar dummy variables, every one must not be free.
That is, it must be true that
(𝜑 → ∀𝑥𝜑) for each setvar dummy variable 𝑥
where 𝜑 is the definiens.
We use two different tests for non-freeness; one must succeed
for each setvar dummy variable 𝑥.
The first test requires that the setvar dummy variable 𝑥
be syntactically bound
(this is sometimes called the "fast" test, and this implies
that we must track binding operators).
The second test requires a successful
search for the directly-stated proof of (𝜑 → ∀𝑥𝜑)
Part c of this rule is how most setvar dummy variables
are handled.
Rule 3 may seem unnecessary, but it is needed.
Without this rule, you can define something like
cbar $a wff Foo x y $.
${ $d x y $. df-foo $a |- ( Foo x y <-> x = y ) $. $}
and now "Foo x x" is not eliminable;
there is no way to prove that it means anything in particular,
because the definitional theorem that is supposed to be
responsible for connecting it to the original language wants
nothing to do with this expression, even though it is well formed.
A justification theorem for a definition (if used this way)
must be proven before the definition that depends on it.
One example of a justification theorem is vjust 3201.
The definition df-v 3202 ⊢ V = {𝑥 ∣ 𝑥 = 𝑥} is justified
by the justification theorem vjust 3201
⊢ {𝑥 ∣ 𝑥 = 𝑥} = {𝑦 ∣ 𝑦 = 𝑦}.
Another example of a justification theorem is trujust 1485;
the definition df-tru 1486 ⊢ (⊤ ↔ (∀𝑥𝑥 = 𝑥 → ∀𝑥𝑥 = 𝑥))
is justified by trujust 1485 ⊢ ((∀𝑥𝑥 = 𝑥 → ∀𝑥𝑥 = 𝑥) ↔ (∀𝑦𝑦 = 𝑦 → ∀𝑦𝑦 = 𝑦)).
Here is more information about our processes for checking and
contributing to this work:
- Multiple verifiers.
This entire file is verified by multiple independently-implemented
verifiers when it is checked in, giving us extremely high
confidence that all proofs follow from the assumptions.
The checkers also check for various other problems such as
overly long lines.
- Maximum text line length is 79 characters.
You can fix comment line length by running the commands scripts/rewrap
or metamath 'read set.mm' 'save proof */c/f'
'write source set.mm/rewrap' quit .
As a general rule, a math string in a comment should be surrounded
by backquotes on the same line, and if it is too long it should
be broken into multiple adjacent mathstrings on multiple lines.
Those commands don't modify the math content of statements.
In statements we try to break before the outermost important connective
(not including the typecode and perhaps not the antecedent).
For examples, see sqrtmulii 14126 and absmax 14069.
- Discouraged information.
A separate file named "discouraged" lists all
discouraged statements and uses of them, and this file is checked.
If you change the use of discouraged things, you will need to change
this file.
This makes it obvious when there is a change to anything discouraged
(triggering further review).
- LRParser check.
Metamath verifiers ensure that $p statements follow from previous
$a and $p statements.
However, by itself the Metamath language permits certain kinds of
syntactic ambiguity that we choose to avoid in this database.
Thus, we require that this database unambiguously parse
using the "LRParser" check (implemented by at least mmj2).
(For details, see mmj2 master file src/mmj/verify/LRParser.java).
This check
counters, for example, a devious ambiguous construct
developed by saueran at oregonstate dot edu
posted on Mon, 11 Feb 2019 17:32:32 -0800 (PST)
based on creating definitions with mismatched parentheses.
- Proposing specific changes.
Please propose specific changes as pull requests (PRs) against the
"develop" branch of set.mm, at:
https://github.com/metamath/set.mm/tree/develop
- Community.
We encourage anyone interested in Metamath to join our mailing list:
https://groups.google.com/forum/#!forum/metamath.
(Contributed by DAW, 27-Dec-2016.) (New usage is discouraged.)
|
⊢ 𝜑 ⇒ ⊢ 𝜑 |
|
Theorem | conventions-label 27259 |
The following explains some of the label conventions in use
in the Metamath Proof Explorer ("set.mm").
For the general conventions, see conventions 27258.
Every statement has a unique identifying label, which serves the
same purpose as an equation number in a book.
We use various label naming conventions to provide
easy-to-remember hints about their contents.
Labels are not a 1-to-1 mapping, because that would create
long names that would be difficult to remember and tedious to type.
Instead, label names are relatively short while
suggesting their purpose.
Names are occasionally changed to make them more consistent or
as we find better ways to name them.
Here are a few of the label naming conventions:
- Axioms, definitions, and wff syntax.
As noted earlier, axioms are named "ax-NAME",
proofs of proven axioms are named "axNAME", and
definitions are named "df-NAME".
Wff syntax declarations have labels beginning with "w"
followed by short fragment suggesting its purpose.
- Hypotheses.
Hypotheses have the name of the final axiom or theorem, followed by
".", followed by a unique id (these ids are usually consecutive integers
starting with 1, e.g. for rgen 2922"rgen.1 $e |- ( x e. A -> ph ) $."
or letters corresponding to the (main) class variable used in the
hypothesis, e.g. for mdet0 20412: "mdet0.d $e |- D = ( N maDet R ) $.").
- Common names.
If a theorem has a well-known name, that name (or a short version of it)
is sometimes used directly. Examples include
barbara 2563 and stirling 40306.
- Principia Mathematica.
Proofs of theorems from Principia Mathematica often use a special
naming convention: "pm" followed by its identifier.
For example, Theorem *2.27 of [WhiteheadRussell] p. 104 is named
pm2.27 42.
- 19.x series of theorems.
Similar to the conventions for the theorems from Principia Mathematica,
theorems from Section 19 of [Margaris] p. 90 often use a special naming
convention: "19." resp. "r19." (for corresponding restricted quantifier
versions) followed by its identifier.
For example, Theorem 38 from Section 19 of [Margaris] p. 90 is labeled
19.38 1766, and the restricted quantifier version of Theorem 21 from
Section 19 of [Margaris] p. 90 is labeled r19.21 2956.
- Characters to be used for labels
Although the specification of Metamath allows for dots/periods "." in
any label, it is usually used only in labels for hypotheses (see above).
Exceptions are the labels of theorems from Principia Mathematica and the
19.x series of theorems from Section 19 of [Margaris] p. 90 (see above)
and 0.999... 14612. Furthermore, the underscore "_" should not be used.
- Syntax label fragments.
Most theorems are named using a concatenation of syntax label fragments
(omitting variables) that represent the important part of the theorem's
main conclusion. Almost every syntactic construct has a definition
labeled "df-NAME", and normally NAME is the syntax label fragment. For
example, the class difference construct (𝐴 ∖ 𝐵) is defined in
df-dif 3577, and thus its syntax label fragment is "dif". Similarly, the
subclass relation 𝐴 ⊆ 𝐵 has syntax label fragment "ss"
because it is defined in df-ss 3588. Most theorem names follow from
these fragments, for example, the theorem proving (𝐴 ∖ 𝐵) ⊆ 𝐴
involves a class difference ("dif") of a subset ("ss"), and thus is
labeled difss 3737. There are many other syntax label fragments, e.g.,
singleton construct {𝐴} has syntax label fragment "sn" (because it
is defined in df-sn 4178), and the pair construct {𝐴, 𝐵} has
fragment "pr" ( from df-pr 4180). Digits are used to represent
themselves. Suffixes (e.g., with numbers) are sometimes used to
distinguish multiple theorems that would otherwise produce the same
label.
- Phantom definitions.
In some cases there are common label fragments for something that could
be in a definition, but for technical reasons is not. The is-element-of
(is member of) construct 𝐴 ∈ 𝐵 does not have a df-NAME definition;
in this case its syntax label fragment is "el". Thus, because the
theorem beginning with (𝐴 ∈ (𝐵 ∖ {𝐶}) uses is-element-of
("el") of a class difference ("dif") of a singleton ("sn"), it is
labeled eldifsn 4317. An "n" is often used for negation (¬), e.g.,
nan 604.
- Exceptions.
Sometimes there is a definition df-NAME but the label fragment is not
the NAME part. The definition should note this exception as part of its
definition. In addition, the table below attempts to list all such
cases and marks them in bold. For example, the label fragment "cn"
represents complex numbers ℂ (even though its definition is in
df-c 9942) and "re" represents real numbers ℝ ( definition df-r 9946).
The empty set ∅ often uses fragment 0, even though it is defined
in df-nul 3916. The syntax construct (𝐴 + 𝐵) usually uses the
fragment "add" (which is consistent with df-add 9947), but "p" is used as
the fragment for constant theorems. Equality (𝐴 = 𝐵) often uses
"e" as the fragment. As a result, "two plus two equals four" is labeled
2p2e4 11144.
- Other markings.
In labels we sometimes use "com" for "commutative", "ass" for
"associative", "rot" for "rotation", and "di" for "distributive".
- Focus on the important part of the conclusion.
Typically the conclusion is the part the user is most interested in.
So, a rough guideline is that a label typically provides a hint
about only the conclusion; a label rarely says anything about the
hypotheses or antecedents.
If there are multiple theorems with the same conclusion
but different hypotheses/antecedents, then the labels will need
to differ; those label differences should emphasize what is different.
There is no need to always fully describe the conclusion; just
identify the important part. For example,
cos0 14880 is the theorem that provides the value for the cosine of 0;
we would need to look at the theorem itself to see what that value is.
The label "cos0" is concise and we use it instead of "cos0eq1".
There is no need to add the "eq1", because there will never be a case
where we have to disambiguate between different values produced by
the cosine of zero, and we generally prefer shorter labels if
they are unambiguous.
- Closures and values.
As noted above, if a function df-NAME is defined, there is typically a
proof of its value labeled "NAMEval" and of its closure labeld "NAMEcl".
E.g., for cosine (df-cos 14801) we have value cosval 14853 and closure
coscl 14857.
- Special cases.
Sometimes, syntax and related markings are insufficient to distinguish
different theorems. For example, there are over a hundred different
implication-only theorems. They are grouped in a more ad-hoc way that
attempts to make their distinctions clearer. These often use
abbreviations such as "mp" for "modus ponens", "syl" for syllogism, and
"id" for "identity". It is especially hard to give good names in the
propositional calculus section because there are so few primitives.
However, in most cases this is not a serious problem. There are a few
very common theorems like ax-mp 5 and syl 17 that you will have no
trouble remembering, a few theorem series like syl*anc and simp* that
you can use parametrically, and a few other useful glue things for
destructuring 'and's and 'or's (see natded 27260 for a list), and that is
about all you need for most things. As for the rest, you can just
assume that if it involves at most three connectives, then it is
probably already proved in set.mm, and searching for it will give you
the label.
- Suffixes.
Suffixes are used to indicate the form of a theorem (see above).
Additionally, we sometimes suffix with "v" the label of a theorem
eliminating a hypothesis such as Ⅎ𝑥𝜑 in 19.21 2075 via the use of
disjoint variable conditions combined with nfv 1843. If two (or three)
such hypotheses are eliminated, the suffix "vv" resp. "vvv" is used,
e.g. exlimivv 1860.
Conversely, we sometimes suffix with "f" the label of a theorem
introducing such a hypothesis to eliminate the need for the disjoint
variable condition; e.g. euf 2478 derived from df-eu 2474. The "f" stands
for "not free in" which is less restrictive than "does not occur in."
The suffix "b" often means "biconditional" (↔, "iff" , "if and
only if"), e.g. sspwb 4917.
We sometimes suffix with "s" the label of an inference that manipulates
an antecedent, leaving the consequent unchanged. The "s" means that the
inference eliminates the need for a syllogism (syl 17) -type inference
in a proof. A theorem label is suffixed with "ALT" if it provides an
alternate less-preferred proof of a theorem (e.g., the proof is
clearer but uses more axioms than the preferred version).
The "ALT" may be further suffixed with a number if there is more
than one alternate theorem.
Furthermore, a theorem label is suffixed with "OLD" if there is a new
version of it and the OLD version is obsolete (and will be removed
within one year).
Finally, it should be mentioned that suffixes can be combined, for
example in cbvaldva 2281 (cbval 2271 in deduction form "d" with a not free
variable replaced by a disjoint variable condition "v" with a
conjunction as antecedent "a"). As a general rule, the suffixes for
the theorem forms ("i", "d" or "g") should be the first of multiple
suffixes, as for example in vtocldf 3256 or rabeqif 3191.
Here is a non-exhaustive list of common suffixes:
- a : theorem having a conjunction as antecedent
- b : theorem expressing a logical equivalence
- c : contraction (e.g., sylc 65, syl2anc 693), commutes
(e.g., biimpac 503)
- d : theorem in deduction form
- f : theorem with a hypothesis such as Ⅎ𝑥𝜑
- g : theorem in closed form having an "is a set" antecedent
- i : theorem in inference form
- l : theorem concerning something at the left
- r : theorem concerning something at the right
- r : theorem with something reversed (e.g., a biconditional)
- s : inference that manipulates an antecedent ("s" refers to an
application of syl 17 that is eliminated)
- v : theorem with one (main) disjoint variable condition
- vv : theorem with two (main) disjoint variable conditions
- w : weak(er) form of a theorem
- ALT : alternate proof of a theorem
- ALTV : alternate version of a theorem or definition
- OLD : old/obsolete version of a theorem/definition/proof
- Reuse.
When creating a new theorem or axiom, try to reuse abbreviations used
elsewhere. A comment should explain the first use of an abbreviation.
The following table shows some commonly used abbreviations in labels, in
alphabetical order. For each abbreviation we provide a mnenomic, the
source theorem or the assumption defining it, an expression showing what
it looks like, whether or not it is a "syntax fragment" (an abbreviation
that indicates a particular kind of syntax), and hyperlinks to label
examples that use the abbreviation. The abbreviation is bolded if there
is a df-NAME definition but the label fragment is not NAME. This is
not a complete list of abbreviations, though we do want this to
eventually be a complete list of exceptions.
Abbreviation | Mnenomic | Source |
Expression | Syntax? | Example(s) |
a | and (suffix) | |
| No | biimpa 501, rexlimiva 3028 |
abl | Abelian group | df-abl 18196 |
Abel | Yes | ablgrp 18198, zringabl 19822 |
abs | absorption | | | No |
ressabs 15939 |
abs | absolute value (of a complex number) |
df-abs 13976 | (abs‘𝐴) | Yes |
absval 13978, absneg 14017, abs1 14037 |
ad | adding | |
| No | adantr 481, ad2antlr 763 |
add | add (see "p") | df-add 9947 |
(𝐴 + 𝐵) | Yes |
addcl 10018, addcom 10222, addass 10023 |
al | "for all" | |
∀𝑥𝜑 | No | alim 1738, alex 1753 |
ALT | alternative/less preferred (suffix) | |
| No | idALT 23 |
an | and | df-an 386 |
(𝜑 ∧ 𝜓) | Yes |
anor 510, iman 440, imnan 438 |
ant | antecedent | |
| No | adantr 481 |
ass | associative | |
| No | biass 374, orass 546, mulass 10024 |
asym | asymmetric, antisymmetric | |
| No | intasym 5511, asymref 5512, posasymb 16952 |
ax | axiom | |
| No | ax6dgen 2005, ax1cn 9970 |
bas, base |
base (set of an extensible structure) | df-base 15863 |
(Base‘𝑆) | Yes |
baseval 15918, ressbas 15930, cnfldbas 19750 |
b, bi | biconditional ("iff", "if and only if")
| df-bi 197 | (𝜑 ↔ 𝜓) | Yes |
impbid 202, sspwb 4917 |
br | binary relation | df-br 4654 |
𝐴𝑅𝐵 | Yes | brab1 4700, brun 4703 |
cbv | change bound variable | | |
No | cbvalivw 1934, cbvrex 3168 |
cl | closure | | | No |
ifclda 4120, ovrcl 6686, zaddcl 11417 |
cn | complex numbers | df-c 9942 |
ℂ | Yes | nnsscn 11025, nncn 11028 |
cnfld | field of complex numbers | df-cnfld 19747 |
ℂfld | Yes | cnfldbas 19750, cnfldinv 19777 |
cntz | centralizer | df-cntz 17750 |
(Cntz‘𝑀) | Yes |
cntzfval 17753, dprdfcntz 18414 |
cnv | converse | df-cnv 5122 |
◡𝐴 | Yes | opelcnvg 5302, f1ocnv 6149 |
co | composition | df-co 5123 |
(𝐴 ∘ 𝐵) | Yes | cnvco 5308, fmptco 6396 |
com | commutative | |
| No | orcom 402, bicomi 214, eqcomi 2631 |
con | contradiction, contraposition | |
| No | condan 835, con2d 129 |
csb | class substitution | df-csb 3534 |
⦋𝐴 / 𝑥⦌𝐵 | Yes |
csbid 3541, csbie2g 3564 |
cyg | cyclic group | df-cyg 18280 |
CycGrp | Yes |
iscyg 18281, zringcyg 19839 |
d | deduction form (suffix) | |
| No | idd 24, impbid 202 |
df | (alternate) definition (prefix) | |
| No | dfrel2 5583, dffn2 6047 |
di, distr | distributive | |
| No |
andi 911, imdi 378, ordi 908, difindi 3881, ndmovdistr 6823 |
dif | class difference | df-dif 3577 |
(𝐴 ∖ 𝐵) | Yes |
difss 3737, difindi 3881 |
div | division | df-div 10685 |
(𝐴 / 𝐵) | Yes |
divcl 10691, divval 10687, divmul 10688 |
dm | domain | df-dm 5124 |
dom 𝐴 | Yes | dmmpt 5630, iswrddm0 13329 |
e, eq, equ | equals | df-cleq 2615 |
𝐴 = 𝐵 | Yes |
2p2e4 11144, uneqri 3755, equtr 1948 |
edg | edge | df-edg 25940 |
(Edg‘𝐺) | Yes |
edgopval 25944, usgredgppr 26088 |
el | element of | |
𝐴 ∈ 𝐵 | Yes |
eldif 3584, eldifsn 4317, elssuni 4467 |
eu | "there exists exactly one" | df-eu 2474 |
∃!𝑥𝜑 | Yes | euex 2494, euabsn 4261 |
ex | exists (i.e. is a set) | |
| No | brrelex 5156, 0ex 4790 |
ex | "there exists (at least one)" | df-ex 1705 |
∃𝑥𝜑 | Yes | exim 1761, alex 1753 |
exp | export | |
| No | expt 168, expcom 451 |
f | "not free in" (suffix) | |
| No | equs45f 2350, sbf 2380 |
f | function | df-f 5892 |
𝐹:𝐴⟶𝐵 | Yes | fssxp 6060, opelf 6065 |
fal | false | df-fal 1489 |
⊥ | Yes | bifal 1497, falantru 1508 |
fi | finite intersection | df-fi 8317 |
(fi‘𝐵) | Yes | fival 8318, inelfi 8324 |
fi, fin | finite | df-fin 7959 |
Fin | Yes |
isfi 7979, snfi 8038, onfin 8151 |
fld | field (Note: there is an alternative
definition Fld of a field, see df-fld 33791) | df-field 18750 |
Field | Yes | isfld 18756, fldidom 19305 |
fn | function with domain | df-fn 5891 |
𝐴 Fn 𝐵 | Yes | ffn 6045, fndm 5990 |
frgp | free group | df-frgp 18123 |
(freeGrp‘𝐼) | Yes |
frgpval 18171, frgpadd 18176 |
fsupp | finitely supported function |
df-fsupp 8276 | 𝑅 finSupp 𝑍 | Yes |
isfsupp 8279, fdmfisuppfi 8284, fsuppco 8307 |
fun | function | df-fun 5890 |
Fun 𝐹 | Yes | funrel 5905, ffun 6048 |
fv | function value | df-fv 5896 |
(𝐹‘𝐴) | Yes | fvres 6207, swrdfv 13424 |
fz | finite set of sequential integers |
df-fz 12327 |
(𝑀...𝑁) | Yes | fzval 12328, eluzfz 12337 |
fz0 | finite set of sequential nonnegative integers |
|
(0...𝑁) | Yes | nn0fz0 12437, fz0tp 12440 |
fzo | half-open integer range | df-fzo 12466 |
(𝑀..^𝑁) | Yes |
elfzo 12472, elfzofz 12485 |
g | more general (suffix); eliminates "is a set"
hypothsis | |
| No | uniexg 6955 |
gr | graph | |
| No | uhgrf 25957, isumgr 25990, usgrres1 26207 |
grp | group | df-grp 17425 |
Grp | Yes | isgrp 17428, tgpgrp 21882 |
gsum | group sum | df-gsum 16103 |
(𝐺 Σg 𝐹) | Yes |
gsumval 17271, gsumwrev 17796 |
hash | size (of a set) | df-hash 13118 |
(#‘𝐴) | Yes |
hashgval 13120, hashfz1 13134, hashcl 13147 |
hb | hypothesis builder (prefix) | |
| No | hbxfrbi 1752, hbald 2041, hbequid 34194 |
hm | (monoid, group, ring) homomorphism | |
| No | ismhm 17337, isghm 17660, isrhm 18721 |
i | inference (suffix) | |
| No | eleq1i 2692, tcsni 8619 |
i | implication (suffix) | |
| No | brwdomi 8473, infeq5i 8533 |
id | identity | |
| No | biid 251 |
iedg | indexed edge | df-iedg 25877 |
(iEdg‘𝐺) | Yes |
iedgval0 25932, edgiedgb 25947 |
idm | idempotent | |
| No | anidm 676, tpidm13 4291 |
im, imp | implication (label often omitted) |
df-im 13841 | (𝐴 → 𝐵) | Yes |
iman 440, imnan 438, impbidd 200 |
ima | image | df-ima 5127 |
(𝐴 “ 𝐵) | Yes | resima 5431, imaundi 5545 |
imp | import | |
| No | biimpa 501, impcom 446 |
in | intersection | df-in 3581 |
(𝐴 ∩ 𝐵) | Yes | elin 3796, incom 3805 |
inf | infimum | df-inf 8349 |
inf(ℝ+, ℝ*, < ) | Yes |
fiinfcl 8407, infiso 8413 |
is... | is (something a) ...? | |
| No | isring 18551 |
j | joining, disjoining | |
| No | jc 159, jaoi 394 |
l | left | |
| No | olcd 408, simpl 473 |
map | mapping operation or set exponentiation |
df-map 7859 | (𝐴 ↑𝑚 𝐵) | Yes |
mapvalg 7867, elmapex 7878 |
mat | matrix | df-mat 20214 |
(𝑁 Mat 𝑅) | Yes |
matval 20217, matring 20249 |
mdet | determinant (of a square matrix) |
df-mdet 20391 | (𝑁 maDet 𝑅) | Yes |
mdetleib 20393, mdetrlin 20408 |
mgm | magma | df-mgm 17242 |
Magma | Yes |
mgmidmo 17259, mgmlrid 17266, ismgm 17243 |
mgp | multiplicative group | df-mgp 18490 |
(mulGrp‘𝑅) | Yes |
mgpress 18500, ringmgp 18553 |
mnd | monoid | df-mnd 17295 |
Mnd | Yes | mndass 17302, mndodcong 17961 |
mo | "there exists at most one" | df-mo 2475 |
∃*𝑥𝜑 | Yes | eumo 2499, moim 2519 |
mp | modus ponens | ax-mp 5 |
| No | mpd 15, mpi 20 |
mpt | modus ponendo tollens | |
| No | mptnan 1693, mptxor 1694 |
mpt | maps-to notation for a function |
df-mpt 4730 | (𝑥 ∈ 𝐴 ↦ 𝐵) | Yes |
fconstmpt 5163, resmpt 5449 |
mpt2 | maps-to notation for an operation |
df-mpt2 6655 | (𝑥 ∈ 𝐴, 𝑦 ∈ 𝐵 ↦ 𝐶) | Yes |
mpt2mpt 6752, resmpt2 6758 |
mul | multiplication (see "t") | df-mul 9948 |
(𝐴 · 𝐵) | Yes |
mulcl 10020, divmul 10688, mulcom 10022, mulass 10024 |
n, not | not | |
¬ 𝜑 | Yes |
nan 604, notnotr 125 |
ne | not equal | df-ne | 𝐴 ≠ 𝐵 |
Yes | exmidne 2804, neeqtrd 2863 |
nel | not element of | df-nel | 𝐴 ∉ 𝐵
|
Yes | neli 2899, nnel 2906 |
ne0 | not equal to zero (see n0) | |
≠ 0 | No |
negne0d 10390, ine0 10465, gt0ne0 10493 |
nf | "not free in" (prefix) | |
| No | nfnd 1785 |
ngp | normed group | df-ngp 22388 |
NrmGrp | Yes | isngp 22400, ngptps 22406 |
nm | norm (on a group or ring) | df-nm 22387 |
(norm‘𝑊) | Yes |
nmval 22394, subgnm 22437 |
nn | positive integers | df-nn 11021 |
ℕ | Yes | nnsscn 11025, nncn 11028 |
nn0 | nonnegative integers | df-n0 11293 |
ℕ0 | Yes | nnnn0 11299, nn0cn 11302 |
n0 | not the empty set (see ne0) | |
≠ ∅ | No | n0i 3920, vn0 3924, ssn0 3976 |
OLD | old, obsolete (to be removed soon) | |
| No | 19.43OLD 1811 |
op | ordered pair | df-op 4184 |
〈𝐴, 𝐵〉 | Yes | dfopif 4399, opth 4945 |
or | or | df-or 385 |
(𝜑 ∨ 𝜓) | Yes |
orcom 402, anor 510 |
ot | ordered triple | df-ot 4186 |
〈𝐴, 𝐵, 𝐶〉 | Yes |
euotd 4975, fnotovb 6694 |
ov | operation value | df-ov 6653 |
(𝐴𝐹𝐵) | Yes
| fnotovb 6694, fnovrn 6809 |
p | plus (see "add"), for all-constant
theorems | df-add 9947 |
(3 + 2) = 5 | Yes |
3p2e5 11160 |
pfx | prefix | df-pfx 41382 |
(𝑊 prefix 𝐿) | Yes |
pfxlen 41391, ccatpfx 41409 |
pm | Principia Mathematica | |
| No | pm2.27 42 |
pm | partial mapping (operation) | df-pm 7860 |
(𝐴 ↑pm 𝐵) | Yes | elpmi 7876, pmsspw 7892 |
pr | pair | df-pr 4180 |
{𝐴, 𝐵} | Yes |
elpr 4198, prcom 4267, prid1g 4295, prnz 4310 |
prm, prime | prime (number) | df-prm 15386 |
ℙ | Yes | 1nprm 15392, dvdsprime 15400 |
pss | proper subset | df-pss 3590 |
𝐴 ⊊ 𝐵 | Yes | pssss 3702, sspsstri 3709 |
q | rational numbers ("quotients") | df-q 11789 |
ℚ | Yes | elq 11790 |
r | right | |
| No | orcd 407, simprl 794 |
rab | restricted class abstraction |
df-rab 2921 | {𝑥 ∈ 𝐴 ∣ 𝜑} | Yes |
rabswap 3121, df-oprab 6654 |
ral | restricted universal quantification |
df-ral 2917 | ∀𝑥 ∈ 𝐴𝜑 | Yes |
ralnex 2992, ralrnmpt2 6775 |
rcl | reverse closure | |
| No | ndmfvrcl 6219, nnarcl 7696 |
re | real numbers | df-r 9946 |
ℝ | Yes | recn 10026, 0re 10040 |
rel | relation | df-rel 5121 | Rel 𝐴 |
Yes | brrelex 5156, relmpt2opab 7259 |
res | restriction | df-res 5126 |
(𝐴 ↾ 𝐵) | Yes |
opelres 5401, f1ores 6151 |
reu | restricted existential uniqueness |
df-reu 2919 | ∃!𝑥 ∈ 𝐴𝜑 | Yes |
nfreud 3112, reurex 3160 |
rex | restricted existential quantification |
df-rex 2918 | ∃𝑥 ∈ 𝐴𝜑 | Yes |
rexnal 2995, rexrnmpt2 6776 |
rmo | restricted "at most one" |
df-rmo 2920 | ∃*𝑥 ∈ 𝐴𝜑 | Yes |
nfrmod 3113, nrexrmo 3163 |
rn | range | df-rn 5125 | ran 𝐴 |
Yes | elrng 5314, rncnvcnv 5349 |
rng | (unital) ring | df-ring 18549 |
Ring | Yes |
ringidval 18503, isring 18551, ringgrp 18552 |
rot | rotation | |
| No | 3anrot 1043, 3orrot 1044 |
s | eliminates need for syllogism (suffix) |
| | No | ancoms 469 |
sb | (proper) substitution (of a set) |
df-sb 1881 | [𝑦 / 𝑥]𝜑 | Yes |
spsbe 1884, sbimi 1886 |
sbc | (proper) substitution of a class |
df-sbc 3436 | [𝐴 / 𝑥]𝜑 | Yes |
sbc2or 3444, sbcth 3450 |
sca | scalar | df-sca 15957 |
(Scalar‘𝐻) | Yes |
resssca 16031, mgpsca 18496 |
simp | simple, simplification | |
| No | simpl 473, simp3r3 1171 |
sn | singleton | df-sn 4178 |
{𝐴} | Yes | eldifsn 4317 |
sp | specialization | |
| No | spsbe 1884, spei 2261 |
ss | subset | df-ss 3588 |
𝐴 ⊆ 𝐵 | Yes | difss 3737 |
struct | structure | df-struct 15859 |
Struct | Yes | brstruct 15866, structfn 15874 |
sub | subtract | df-sub 10268 |
(𝐴 − 𝐵) | Yes |
subval 10272, subaddi 10368 |
sup | supremum | df-sup 8348 |
sup(𝐴, 𝐵, < ) | Yes |
fisupcl 8375, supmo 8358 |
supp | support (of a function) | df-supp 7296 |
(𝐹 supp 𝑍) | Yes |
ressuppfi 8301, mptsuppd 7318 |
swap | swap (two parts within a theorem) |
| | No | rabswap 3121, 2reuswap 3410 |
syl | syllogism | syl 17 |
| No | 3syl 18 |
sym | symmetric | |
| No | df-symdif 3844, cnvsym 5510 |
symg | symmetric group | df-symg 17798 |
(SymGrp‘𝐴) | Yes |
symghash 17805, pgrpsubgsymg 17828 |
t |
times (see "mul"), for all-constant theorems |
df-mul 9948 |
(3 · 2) = 6 | Yes |
3t2e6 11179 |
th | theorem | |
| No | nfth 1727, sbcth 3450, weth 9317 |
tp | triple | df-tp 4182 |
{𝐴, 𝐵, 𝐶} | Yes |
eltpi 4229, tpeq1 4277 |
tr | transitive | |
| No | bitrd 268, biantr 972 |
tru | true | df-tru 1486 |
⊤ | Yes | bitru 1496, truanfal 1507 |
un | union | df-un 3579 |
(𝐴 ∪ 𝐵) | Yes |
uneqri 3755, uncom 3757 |
unit | unit (in a ring) |
df-unit 18642 | (Unit‘𝑅) | Yes |
isunit 18657, nzrunit 19267 |
v | disjoint variable conditions used when
a not-free hypothesis (suffix) |
| | No | spimv 2257 |
vtx | vertex | df-vtx 25876 |
(Vtx‘𝐺) | Yes |
vtxval0 25931, opvtxov 25885 |
vv | 2 disjoint variables (in a not-free hypothesis)
(suffix) | | | No | 19.23vv 1903 |
w | weak (version of a theorem) (suffix) | |
| No | ax11w 2007, spnfw 1928 |
wrd | word |
df-word 13299 | Word 𝑆 | Yes |
iswrdb 13311, wrdfn 13319, ffz0iswrd 13332 |
xp | cross product (Cartesian product) |
df-xp 5120 | (𝐴 × 𝐵) | Yes |
elxp 5131, opelxpi 5148, xpundi 5171 |
xr | eXtended reals | df-xr 10078 |
ℝ* | Yes | ressxr 10083, rexr 10085, 0xr 10086 |
z | integers (from German "Zahlen") |
df-z 11378 | ℤ | Yes |
elz 11379, zcn 11382 |
zn | ring of integers mod 𝑛 | df-zn 19855 |
(ℤ/nℤ‘𝑁) | Yes |
znval 19883, zncrng 19893, znhash 19907 |
zring | ring of integers | df-zring 19819 |
ℤring | Yes | zringbas 19824, zringcrng 19820
|
0, z |
slashed zero (empty set) (see n0) | df-nul 3916 |
∅ | Yes |
n0i 3920, vn0 3924; snnz 4309, prnz 4310 |
(Contributed by DAW, 27-Dec-2016.) (New usage is discouraged.)
|
⊢ 𝜑 ⇒ ⊢ 𝜑 |
|
17.1.2 Natural deduction
|
|
Theorem | natded 27260 |
Here are typical natural deduction (ND) rules in the style of Gentzen
and Jaśkowski, along with MPE translations of them. This also
shows the recommended theorems when you find yourself needing these
rules (the recommendations encourage a slightly different proof style
that works more naturally with metamath). A decent list of the standard
rules of natural deduction can be found beginning with definition /\I in
[Pfenning] p. 18. For information about ND and Metamath, see the
page on Deduction Form and Natural Deduction
in Metamath Proof Explorer. Many more citations could be added.
Name | Natural Deduction Rule | Translation |
Recommendation | Comments |
IT |
Γ⊢ 𝜓 => Γ⊢ 𝜓 |
idi 2 |
nothing | Reiteration is always redundant in Metamath.
Definition "new rule" in [Pfenning] p. 18,
definition IT in [Clemente] p. 10. |
∧I |
Γ⊢ 𝜓 & Γ⊢ 𝜒 => Γ⊢ 𝜓 ∧ 𝜒 |
jca 554 |
jca 554, pm3.2i 471 |
Definition ∧I in [Pfenning] p. 18,
definition I∧m,n in [Clemente] p. 10, and
definition ∧I in [Indrzejczak] p. 34
(representing both Gentzen's system NK and Jaśkowski) |
∧EL |
Γ⊢ 𝜓 ∧ 𝜒 => Γ⊢ 𝜓 |
simpld 475 |
simpld 475, adantr 481 |
Definition ∧EL in [Pfenning] p. 18,
definition E∧(1) in [Clemente] p. 11, and
definition ∧E in [Indrzejczak] p. 34
(representing both Gentzen's system NK and Jaśkowski) |
∧ER |
Γ⊢ 𝜓 ∧ 𝜒 => Γ⊢ 𝜒 |
simprd 479 |
simpr 477, adantl 482 |
Definition ∧ER in [Pfenning] p. 18,
definition E∧(2) in [Clemente] p. 11, and
definition ∧E in [Indrzejczak] p. 34
(representing both Gentzen's system NK and Jaśkowski) |
→I |
Γ, 𝜓⊢ 𝜒 => Γ⊢ 𝜓 → 𝜒 |
ex 450 | ex 450 |
Definition →I in [Pfenning] p. 18,
definition I=>m,n in [Clemente] p. 11, and
definition →I in [Indrzejczak] p. 33. |
→E |
Γ⊢ 𝜓 → 𝜒 & Γ⊢ 𝜓 => Γ⊢ 𝜒 |
mpd 15 | ax-mp 5, mpd 15, mpdan 702, imp 445 |
Definition →E in [Pfenning] p. 18,
definition E=>m,n in [Clemente] p. 11, and
definition →E in [Indrzejczak] p. 33. |
∨IL | Γ⊢ 𝜓 =>
Γ⊢ 𝜓 ∨ 𝜒 |
olcd 408 |
olc 399, olci 406, olcd 408 |
Definition ∨I in [Pfenning] p. 18,
definition I∨n(1) in [Clemente] p. 12 |
∨IR | Γ⊢ 𝜒 =>
Γ⊢ 𝜓 ∨ 𝜒 |
orcd 407 |
orc 400, orci 405, orcd 407 |
Definition ∨IR in [Pfenning] p. 18,
definition I∨n(2) in [Clemente] p. 12. |
∨E | Γ⊢ 𝜓 ∨ 𝜒 & Γ, 𝜓⊢ 𝜃 &
Γ, 𝜒⊢ 𝜃 => Γ⊢ 𝜃 |
mpjaodan 827 |
mpjaodan 827, jaodan 826, jaod 395 |
Definition ∨E in [Pfenning] p. 18,
definition E∨m,n,p in [Clemente] p. 12. |
¬I | Γ, 𝜓⊢ ⊥ => Γ⊢ ¬ 𝜓 |
inegd 1503 | pm2.01d 181 |
|
¬I | Γ, 𝜓⊢ 𝜃 & Γ⊢ ¬ 𝜃 =>
Γ⊢ ¬ 𝜓 |
mtand 691 | mtand 691 |
definition I¬m,n,p in [Clemente] p. 13. |
¬I | Γ, 𝜓⊢ 𝜒 & Γ, 𝜓⊢ ¬ 𝜒 =>
Γ⊢ ¬ 𝜓 |
pm2.65da 600 | pm2.65da 600 |
Contradiction. |
¬I |
Γ, 𝜓⊢ ¬ 𝜓 => Γ⊢ ¬ 𝜓 |
pm2.01da 458 | pm2.01d 181, pm2.65da 600, pm2.65d 187 |
For an alternative falsum-free natural deduction ruleset |
¬E |
Γ⊢ 𝜓 & Γ⊢ ¬ 𝜓 => Γ⊢ ⊥ |
pm2.21fal 1505 |
pm2.21dd 186 | |
¬E |
Γ, ¬ 𝜓⊢ ⊥ => Γ⊢ 𝜓 |
|
pm2.21dd 186 |
definition →E in [Indrzejczak] p. 33. |
¬E |
Γ⊢ 𝜓 & Γ⊢ ¬ 𝜓 => Γ⊢ 𝜃 |
pm2.21dd 186 | pm2.21dd 186, pm2.21d 118, pm2.21 120 |
For an alternative falsum-free natural deduction ruleset.
Definition ¬E in [Pfenning] p. 18. |
⊤I | Γ⊢ ⊤ |
a1tru 1500 | tru 1487, a1tru 1500, trud 1493 |
Definition ⊤I in [Pfenning] p. 18. |
⊥E | Γ, ⊥⊢ 𝜃 |
falimd 1499 | falim 1498 |
Definition ⊥E in [Pfenning] p. 18. |
∀I |
Γ⊢ [𝑎 / 𝑥]𝜓 => Γ⊢ ∀𝑥𝜓 |
alrimiv 1855 | alrimiv 1855, ralrimiva 2966 |
Definition ∀Ia in [Pfenning] p. 18,
definition I∀n in [Clemente] p. 32. |
∀E |
Γ⊢ ∀𝑥𝜓 => Γ⊢ [𝑡 / 𝑥]𝜓 |
spsbcd 3449 | spcv 3299, rspcv 3305 |
Definition ∀E in [Pfenning] p. 18,
definition E∀n,t in [Clemente] p. 32. |
∃I |
Γ⊢ [𝑡 / 𝑥]𝜓 => Γ⊢ ∃𝑥𝜓 |
spesbcd 3522 | spcev 3300, rspcev 3309 |
Definition ∃I in [Pfenning] p. 18,
definition I∃n,t in [Clemente] p. 32. |
∃E |
Γ⊢ ∃𝑥𝜓 & Γ, [𝑎 / 𝑥]𝜓⊢ 𝜃 =>
Γ⊢ 𝜃 |
exlimddv 1863 | exlimddv 1863, exlimdd 2088,
exlimdv 1861, rexlimdva 3031 |
Definition ∃Ea,u in [Pfenning] p. 18,
definition E∃m,n,p,a in [Clemente] p. 32. |
⊥C |
Γ, ¬ 𝜓⊢ ⊥ => Γ⊢ 𝜓 |
efald 1504 | efald 1504 |
Proof by contradiction (classical logic),
definition ⊥C in [Pfenning] p. 17. |
⊥C |
Γ, ¬ 𝜓⊢ 𝜓 => Γ⊢ 𝜓 |
pm2.18da 459 | pm2.18da 459, pm2.18d 124, pm2.18 122 |
For an alternative falsum-free natural deduction ruleset |
¬ ¬C |
Γ⊢ ¬ ¬ 𝜓 => Γ⊢ 𝜓 |
notnotrd 128 | notnotrd 128, notnotr 125 |
Double negation rule (classical logic),
definition NNC in [Pfenning] p. 17,
definition E¬n in [Clemente] p. 14. |
EM | Γ⊢ 𝜓 ∨ ¬ 𝜓 |
exmidd 432 | exmid 431 |
Excluded middle (classical logic),
definition XM in [Pfenning] p. 17,
proof 5.11 in [Clemente] p. 14. |
=I | Γ⊢ 𝐴 = 𝐴 |
eqidd 2623 | eqid 2622, eqidd 2623 |
Introduce equality,
definition =I in [Pfenning] p. 127. |
=E | Γ⊢ 𝐴 = 𝐵 & Γ[𝐴 / 𝑥]𝜓 =>
Γ⊢ [𝐵 / 𝑥]𝜓 |
sbceq1dd 3441 | sbceq1d 3440, equality theorems |
Eliminate equality,
definition =E in [Pfenning] p. 127. (Both E1 and E2.) |
Note that MPE uses classical logic, not intuitionist logic. As is
conventional, the "I" rules are introduction rules, "E" rules are
elimination rules, the "C" rules are conversion rules, and Γ
represents the set of (current) hypotheses. We use wff variable names
beginning with 𝜓 to provide a closer representation
of the Metamath
equivalents (which typically use the antedent 𝜑 to represent the
context Γ).
Most of this information was developed by Mario Carneiro and posted on
3-Feb-2017. For more information, see the
page on Deduction Form and Natural Deduction
in Metamath Proof Explorer.
For annotated examples where some traditional ND rules
are directly applied in MPE, see ex-natded5.2 27261, ex-natded5.3 27264,
ex-natded5.5 27267, ex-natded5.7 27268, ex-natded5.8 27270, ex-natded5.13 27272,
ex-natded9.20 27274, and ex-natded9.26 27276.
(Contributed by DAW, 4-Feb-2017.) (New usage is discouraged.)
|
⊢ 𝜑 ⇒ ⊢ 𝜑 |
|
17.1.3 Natural deduction examples
These are examples of how natural deduction rules can be applied in Metamath
(both as line-for-line translations of ND rules, and as a way to apply
deduction forms without being limited to applying ND rules). For more
information, see natded 27260 and mmnatded.html 27260. Since these examples should
not be used within proofs of other theorems, especially in Mathboxes, they
are marked with "(New usage is discouraged.)".
|
|
Theorem | ex-natded5.2 27261 |
Theorem 5.2 of [Clemente] p. 15, translated line by line using the
interpretation of natural deduction in Metamath.
For information about ND and Metamath, see the
page on Deduction Form and Natural Deduction
in Metamath Proof Explorer.
The original proof, which uses Fitch style, was written as follows:
# | MPE# | ND Expression |
MPE Translation | ND Rationale |
MPE Rationale |
1 | 5 | ((𝜓 ∧ 𝜒) → 𝜃) |
(𝜑 → ((𝜓 ∧ 𝜒) → 𝜃)) |
Given |
$e. |
2 | 2 | (𝜒 → 𝜓) |
(𝜑 → (𝜒 → 𝜓)) |
Given |
$e. |
3 | 1 | 𝜒 |
(𝜑 → 𝜒) |
Given |
$e. |
4 | 3 | 𝜓 |
(𝜑 → 𝜓) |
→E 2,3 |
mpd 15, the MPE equivalent of →E, 1,2 |
5 | 4 | (𝜓 ∧ 𝜒) |
(𝜑 → (𝜓 ∧ 𝜒)) |
∧I 4,3 |
jca 554, the MPE equivalent of ∧I, 3,1 |
6 | 6 | 𝜃 |
(𝜑 → 𝜃) |
→E 1,5 |
mpd 15, the MPE equivalent of →E, 4,5 |
The original used Latin letters for predicates;
we have replaced them with
Greek letters to follow Metamath naming conventions and so that
it is easier to follow the Metamath translation.
The Metamath line-for-line translation of this
natural deduction approach precedes every line with an antecedent
including 𝜑 and uses the Metamath equivalents
of the natural deduction rules.
Below is the final metamath proof (which reorders some steps).
A much more efficient proof, using more of Metamath and MPE's
capabilities, is shown in ex-natded5.2-2 27262.
A proof without context is shown in ex-natded5.2i 27263.
(Contributed by Mario Carneiro, 9-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → ((𝜓 ∧ 𝜒) → 𝜃)) & ⊢ (𝜑 → (𝜒 → 𝜓)) & ⊢ (𝜑 → 𝜒) ⇒ ⊢ (𝜑 → 𝜃) |
|
Theorem | ex-natded5.2-2 27262 |
A more efficient proof of Theorem 5.2 of [Clemente] p. 15. Compare with
ex-natded5.2 27261 and ex-natded5.2i 27263. (Contributed by Mario Carneiro,
9-Feb-2017.) (Proof modification is discouraged.)
(New usage is discouraged.)
|
⊢ (𝜑 → ((𝜓 ∧ 𝜒) → 𝜃)) & ⊢ (𝜑 → (𝜒 → 𝜓)) & ⊢ (𝜑 → 𝜒) ⇒ ⊢ (𝜑 → 𝜃) |
|
Theorem | ex-natded5.2i 27263 |
The same as ex-natded5.2 27261 and ex-natded5.2-2 27262 but with no context.
(Contributed by Mario Carneiro, 9-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ ((𝜓 ∧ 𝜒) → 𝜃)
& ⊢ (𝜒 → 𝜓)
& ⊢ 𝜒 ⇒ ⊢ 𝜃 |
|
Theorem | ex-natded5.3 27264 |
Theorem 5.3 of [Clemente] p. 16, translated line by line using an
interpretation of natural deduction in Metamath.
A much more efficient proof, using more of Metamath and MPE's
capabilities, is shown in ex-natded5.3-2 27265.
A proof without context is shown in ex-natded5.3i 27266.
For information about ND and Metamath, see the
page on Deduction Form and Natural Deduction
in Metamath Proof Explorer
.
The original proof, which uses Fitch style, was written as follows:
# | MPE# | ND Expression |
MPE Translation | ND Rationale |
MPE Rationale |
1 | 2;3 | (𝜓 → 𝜒) |
(𝜑 → (𝜓 → 𝜒)) |
Given |
$e; adantr 481 to move it into the ND hypothesis |
2 | 5;6 | (𝜒 → 𝜃) |
(𝜑 → (𝜒 → 𝜃)) |
Given |
$e; adantr 481 to move it into the ND hypothesis |
3 | 1 | ...| 𝜓 |
((𝜑 ∧ 𝜓) → 𝜓) |
ND hypothesis assumption |
simpr 477, to access the new assumption |
4 | 4 | ... 𝜒 |
((𝜑 ∧ 𝜓) → 𝜒) |
→E 1,3 |
mpd 15, the MPE equivalent of →E, 1.3.
adantr 481 was used to transform its dependency
(we could also use imp 445 to get this directly from 1)
|
5 | 7 | ... 𝜃 |
((𝜑 ∧ 𝜓) → 𝜃) |
→E 2,4 |
mpd 15, the MPE equivalent of →E, 4,6.
adantr 481 was used to transform its dependency |
6 | 8 | ... (𝜒 ∧ 𝜃) |
((𝜑 ∧ 𝜓) → (𝜒 ∧ 𝜃)) |
∧I 4,5 |
jca 554, the MPE equivalent of ∧I, 4,7 |
7 | 9 | (𝜓 → (𝜒 ∧ 𝜃)) |
(𝜑 → (𝜓 → (𝜒 ∧ 𝜃))) |
→I 3,6 |
ex 450, the MPE equivalent of →I, 8 |
The original used Latin letters for predicates;
we have replaced them with
Greek letters to follow Metamath naming conventions and so that
it is easier to follow the Metamath translation.
The Metamath line-for-line translation of this
natural deduction approach precedes every line with an antecedent
including 𝜑 and uses the Metamath equivalents
of the natural deduction rules.
(Contributed by Mario Carneiro, 9-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → (𝜓 → 𝜒)) & ⊢ (𝜑 → (𝜒 → 𝜃)) ⇒ ⊢ (𝜑 → (𝜓 → (𝜒 ∧ 𝜃))) |
|
Theorem | ex-natded5.3-2 27265 |
A more efficient proof of Theorem 5.3 of [Clemente] p. 16. Compare with
ex-natded5.3 27264 and ex-natded5.3i 27266. (Contributed by Mario Carneiro,
9-Feb-2017.) (Proof modification is discouraged.)
(New usage is discouraged.)
|
⊢ (𝜑 → (𝜓 → 𝜒)) & ⊢ (𝜑 → (𝜒 → 𝜃)) ⇒ ⊢ (𝜑 → (𝜓 → (𝜒 ∧ 𝜃))) |
|
Theorem | ex-natded5.3i 27266 |
The same as ex-natded5.3 27264 and ex-natded5.3-2 27265 but with no context.
Identical to jccir 562, which should be used instead. (Contributed
by
Mario Carneiro, 9-Feb-2017.) (Proof modification is discouraged.)
(New usage is discouraged.)
|
⊢ (𝜓 → 𝜒)
& ⊢ (𝜒 → 𝜃) ⇒ ⊢ (𝜓 → (𝜒 ∧ 𝜃)) |
|
Theorem | ex-natded5.5 27267 |
Theorem 5.5 of [Clemente] p. 18, translated line by line using the
usual translation of natural deduction (ND) in the
Metamath Proof Explorer (MPE) notation.
For information about ND and Metamath, see the
page on Deduction Form and Natural Deduction
in Metamath Proof Explorer.
The original proof, which uses Fitch style, was written as follows
(the leading "..." shows an embedded ND hypothesis, beginning with
the initial assumption of the ND hypothesis):
# | MPE# | ND Expression |
MPE Translation | ND Rationale |
MPE Rationale |
1 | 2;3 |
(𝜓 → 𝜒) |
(𝜑 → (𝜓 → 𝜒)) |
Given |
$e; adantr 481 to move it into the ND hypothesis |
2 | 5 | ¬ 𝜒 |
(𝜑 → ¬ 𝜒) | Given |
$e; we'll use adantr 481 to move it into the ND hypothesis |
3 | 1 |
...| 𝜓 | ((𝜑 ∧ 𝜓) → 𝜓) |
ND hypothesis assumption |
simpr 477 |
4 | 4 | ... 𝜒 |
((𝜑 ∧ 𝜓) → 𝜒) |
→E 1,3 |
mpd 15 1,3 |
5 | 6 | ... ¬ 𝜒 |
((𝜑 ∧ 𝜓) → ¬ 𝜒) |
IT 2 |
adantr 481 5 |
6 | 7 | ¬ 𝜓 |
(𝜑 → ¬ 𝜓) |
∧I 3,4,5 |
pm2.65da 600 4,6 |
The original used Latin letters; we have replaced them with
Greek letters to follow Metamath naming conventions and so that
it is easier to follow the Metamath translation.
The Metamath line-for-line translation of this
natural deduction approach precedes every line with an antecedent
including 𝜑 and uses the Metamath equivalents
of the natural deduction rules.
To add an assumption, the antecedent is modified to include it
(typically by using adantr 481; simpr 477 is useful when you want to
depend directly on the new assumption).
Below is the final metamath proof (which reorders some steps).
A much more efficient proof is mtod 189;
a proof without context is shown in mto 188.
(Contributed by David A. Wheeler, 19-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → (𝜓 → 𝜒)) & ⊢ (𝜑 → ¬ 𝜒) ⇒ ⊢ (𝜑 → ¬ 𝜓) |
|
Theorem | ex-natded5.7 27268 |
Theorem 5.7 of [Clemente] p. 19, translated line by line using the
interpretation of natural deduction in Metamath.
A much more efficient proof, using more of Metamath and MPE's
capabilities, is shown in ex-natded5.7-2 27269.
For information about ND and Metamath, see the
page on Deduction Form and Natural Deduction
in Metamath Proof Explorer
.
The original proof, which uses Fitch style, was written as follows:
# | MPE# | ND Expression |
MPE Translation | ND Rationale |
MPE Rationale |
1 | 6 |
(𝜓 ∨ (𝜒 ∧ 𝜃)) |
(𝜑 → (𝜓 ∨ (𝜒 ∧ 𝜃))) |
Given |
$e. No need for adantr 481 because we do not move this
into an ND hypothesis |
2 | 1 | ...| 𝜓 |
((𝜑 ∧ 𝜓) → 𝜓) |
ND hypothesis assumption (new scope) |
simpr 477 |
3 | 2 | ... (𝜓 ∨ 𝜒) |
((𝜑 ∧ 𝜓) → (𝜓 ∨ 𝜒)) |
∨IL 2 |
orcd 407, the MPE equivalent of ∨IL, 1 |
4 | 3 | ...| (𝜒 ∧ 𝜃) |
((𝜑 ∧ (𝜒 ∧ 𝜃)) → (𝜒 ∧ 𝜃)) |
ND hypothesis assumption (new scope) |
simpr 477 |
5 | 4 | ... 𝜒 |
((𝜑 ∧ (𝜒 ∧ 𝜃)) → 𝜒) |
∧EL 4 |
simpld 475, the MPE equivalent of ∧EL, 3 |
6 | 6 | ... (𝜓 ∨ 𝜒) |
((𝜑 ∧ (𝜒 ∧ 𝜃)) → (𝜓 ∨ 𝜒)) |
∨IR 5 |
olcd 408, the MPE equivalent of ∨IR, 4 |
7 | 7 | (𝜓 ∨ 𝜒) |
(𝜑 → (𝜓 ∨ 𝜒)) |
∨E 1,3,6 |
mpjaodan 827, the MPE equivalent of ∨E, 2,5,6 |
The original used Latin letters for predicates;
we have replaced them with
Greek letters to follow Metamath naming conventions and so that
it is easier to follow the Metamath translation.
The Metamath line-for-line translation of this
natural deduction approach precedes every line with an antecedent
including 𝜑 and uses the Metamath equivalents
of the natural deduction rules.
(Contributed by Mario Carneiro, 9-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → (𝜓 ∨ (𝜒 ∧ 𝜃))) ⇒ ⊢ (𝜑 → (𝜓 ∨ 𝜒)) |
|
Theorem | ex-natded5.7-2 27269 |
A more efficient proof of Theorem 5.7 of [Clemente] p. 19. Compare with
ex-natded5.7 27268. (Contributed by Mario Carneiro,
9-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → (𝜓 ∨ (𝜒 ∧ 𝜃))) ⇒ ⊢ (𝜑 → (𝜓 ∨ 𝜒)) |
|
Theorem | ex-natded5.8 27270 |
Theorem 5.8 of [Clemente] p. 20, translated line by line using the
usual translation of natural deduction (ND) in the
Metamath Proof Explorer (MPE) notation.
For information about ND and Metamath, see the
page on Deduction Form and Natural Deduction
in Metamath Proof Explorer.
The original proof, which uses Fitch style, was written as follows
(the leading "..." shows an embedded ND hypothesis, beginning with
the initial assumption of the ND hypothesis):
# | MPE# | ND Expression |
MPE Translation | ND Rationale |
MPE Rationale |
1 | 10;11 |
((𝜓 ∧ 𝜒) → ¬ 𝜃) |
(𝜑 → ((𝜓 ∧ 𝜒) → ¬ 𝜃)) |
Given |
$e; adantr 481 to move it into the ND hypothesis |
2 | 3;4 | (𝜏 → 𝜃) |
(𝜑 → (𝜏 → 𝜃)) | Given |
$e; adantr 481 to move it into the ND hypothesis |
3 | 7;8 |
𝜒 | (𝜑 → 𝜒) |
Given |
$e; adantr 481 to move it into the ND hypothesis |
4 | 1;2 | 𝜏 | (𝜑 → 𝜏) |
Given |
$e. adantr 481 to move it into the ND hypothesis |
5 | 6 | ...| 𝜓 |
((𝜑 ∧ 𝜓) → 𝜓) |
ND Hypothesis/Assumption |
simpr 477. New ND hypothesis scope, each reference outside
the scope must change antecedent 𝜑 to (𝜑 ∧ 𝜓). |
6 | 9 | ... (𝜓 ∧ 𝜒) |
((𝜑 ∧ 𝜓) → (𝜓 ∧ 𝜒)) |
∧I 5,3 |
jca 554 (∧I), 6,8 (adantr 481 to bring in scope) |
7 | 5 | ... ¬ 𝜃 |
((𝜑 ∧ 𝜓) → ¬ 𝜃) |
→E 1,6 |
mpd 15 (→E), 2,4 |
8 | 12 | ... 𝜃 |
((𝜑 ∧ 𝜓) → 𝜃) |
→E 2,4 |
mpd 15 (→E), 9,11;
note the contradiction with ND line 7 (MPE line 5) |
9 | 13 | ¬ 𝜓 |
(𝜑 → ¬ 𝜓) |
¬I 5,7,8 |
pm2.65da 600 (¬I), 5,12; proof by contradiction.
MPE step 6 (ND#5) does not need a reference here, because
the assumption is embedded in the antecedents |
The original used Latin letters; we have replaced them with
Greek letters to follow Metamath naming conventions and so that
it is easier to follow the Metamath translation.
The Metamath line-for-line translation of this
natural deduction approach precedes every line with an antecedent
including 𝜑 and uses the Metamath equivalents
of the natural deduction rules.
To add an assumption, the antecedent is modified to include it
(typically by using adantr 481; simpr 477 is useful when you want to
depend directly on the new assumption).
Below is the final metamath proof (which reorders some steps).
A much more efficient proof, using more of Metamath and MPE's
capabilities, is shown in ex-natded5.8-2 27271.
(Contributed by Mario Carneiro, 9-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → ((𝜓 ∧ 𝜒) → ¬ 𝜃)) & ⊢ (𝜑 → (𝜏 → 𝜃)) & ⊢ (𝜑 → 𝜒)
& ⊢ (𝜑 → 𝜏) ⇒ ⊢ (𝜑 → ¬ 𝜓) |
|
Theorem | ex-natded5.8-2 27271 |
A more efficient proof of Theorem 5.8 of [Clemente] p. 20. For a longer
line-by-line translation, see ex-natded5.8 27270. (Contributed by Mario
Carneiro, 9-Feb-2017.) (Proof modification is discouraged.)
(New usage is discouraged.)
|
⊢ (𝜑 → ((𝜓 ∧ 𝜒) → ¬ 𝜃)) & ⊢ (𝜑 → (𝜏 → 𝜃)) & ⊢ (𝜑 → 𝜒)
& ⊢ (𝜑 → 𝜏) ⇒ ⊢ (𝜑 → ¬ 𝜓) |
|
Theorem | ex-natded5.13 27272 |
Theorem 5.13 of [Clemente] p. 20, translated line by line using the
interpretation of natural deduction in Metamath.
For information about ND and Metamath, see the
page on Deduction Form and Natural Deduction
in Metamath Proof Explorer.
A much more efficient proof, using more of Metamath and MPE's
capabilities, is shown in ex-natded5.13-2 27273.
The original proof, which uses Fitch style, was written as follows
(the leading "..." shows an embedded ND hypothesis, beginning with
the initial assumption of the ND hypothesis):
# | MPE# | ND Expression |
MPE Translation | ND Rationale |
MPE Rationale |
1 | 15 | (𝜓 ∨ 𝜒) |
(𝜑 → (𝜓 ∨ 𝜒)) |
Given |
$e. |
2;3 | 2 | (𝜓 → 𝜃) |
(𝜑 → (𝜓 → 𝜃)) | Given |
$e. adantr 481 to move it into the ND hypothesis |
3 | 9 | (¬ 𝜏 → ¬ 𝜒) |
(𝜑 → (¬ 𝜏 → ¬ 𝜒)) |
Given |
$e. ad2antrr 762 to move it into the ND sub-hypothesis |
4 | 1 | ...| 𝜓 |
((𝜑 ∧ 𝜓) → 𝜓) |
ND hypothesis assumption |
simpr 477 |
5 | 4 | ... 𝜃 |
((𝜑 ∧ 𝜓) → 𝜃) |
→E 2,4 |
mpd 15 1,3 |
6 | 5 | ... (𝜃 ∨ 𝜏) |
((𝜑 ∧ 𝜓) → (𝜃 ∨ 𝜏)) |
∨I 5 |
orcd 407 4 |
7 | 6 | ...| 𝜒 |
((𝜑 ∧ 𝜒) → 𝜒) |
ND hypothesis assumption |
simpr 477 |
8 | 8 | ... ...| ¬ 𝜏 |
(((𝜑 ∧ 𝜒) ∧ ¬ 𝜏) → ¬ 𝜏) |
(sub) ND hypothesis assumption |
simpr 477 |
9 | 11 | ... ... ¬ 𝜒 |
(((𝜑 ∧ 𝜒) ∧ ¬ 𝜏) → ¬ 𝜒) |
→E 3,8 |
mpd 15 8,10 |
10 | 7 | ... ... 𝜒 |
(((𝜑 ∧ 𝜒) ∧ ¬ 𝜏) → 𝜒) |
IT 7 |
adantr 481 6 |
11 | 12 | ... ¬ ¬ 𝜏 |
((𝜑 ∧ 𝜒) → ¬ ¬ 𝜏) |
¬I 8,9,10 |
pm2.65da 600 7,11 |
12 | 13 | ... 𝜏 |
((𝜑 ∧ 𝜒) → 𝜏) |
¬E 11 |
notnotrd 128 12 |
13 | 14 | ... (𝜃 ∨ 𝜏) |
((𝜑 ∧ 𝜒) → (𝜃 ∨ 𝜏)) |
∨I 12 |
olcd 408 13 |
14 | 16 | (𝜃 ∨ 𝜏) |
(𝜑 → (𝜃 ∨ 𝜏)) |
∨E 1,6,13 |
mpjaodan 827 5,14,15 |
The original used Latin letters; we have replaced them with
Greek letters to follow Metamath naming conventions and so that
it is easier to follow the Metamath translation.
The Metamath line-for-line translation of this
natural deduction approach precedes every line with an antecedent
including 𝜑 and uses the Metamath equivalents
of the natural deduction rules.
To add an assumption, the antecedent is modified to include it
(typically by using adantr 481; simpr 477 is useful when you want to
depend directly on the new assumption).
(Contributed by Mario Carneiro, 9-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → (𝜓 ∨ 𝜒)) & ⊢ (𝜑 → (𝜓 → 𝜃)) & ⊢ (𝜑 → (¬ 𝜏 → ¬ 𝜒)) ⇒ ⊢ (𝜑 → (𝜃 ∨ 𝜏)) |
|
Theorem | ex-natded5.13-2 27273 |
A more efficient proof of Theorem 5.13 of [Clemente] p. 20. Compare
with ex-natded5.13 27272. (Contributed by Mario Carneiro,
9-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → (𝜓 ∨ 𝜒)) & ⊢ (𝜑 → (𝜓 → 𝜃)) & ⊢ (𝜑 → (¬ 𝜏 → ¬ 𝜒)) ⇒ ⊢ (𝜑 → (𝜃 ∨ 𝜏)) |
|
Theorem | ex-natded9.20 27274 |
Theorem 9.20 of [Clemente] p. 43, translated line by line using the
usual translation of natural deduction (ND) in the
Metamath Proof Explorer (MPE) notation.
For information about ND and Metamath, see the
page on Deduction Form and Natural Deduction
in Metamath Proof Explorer.
The original proof, which uses Fitch style, was written as follows
(the leading "..." shows an embedded ND hypothesis, beginning with
the initial assumption of the ND hypothesis):
# | MPE# | ND Expression |
MPE Translation | ND Rationale |
MPE Rationale |
1 | 1 |
(𝜓 ∧ (𝜒 ∨ 𝜃)) |
(𝜑 → (𝜓 ∧ (𝜒 ∨ 𝜃))) |
Given |
$e |
2 | 2 | 𝜓 |
(𝜑 → 𝜓) |
∧EL 1 |
simpld 475 1 |
3 | 11 |
(𝜒 ∨ 𝜃) |
(𝜑 → (𝜒 ∨ 𝜃)) |
∧ER 1 |
simprd 479 1 |
4 | 4 |
...| 𝜒 |
((𝜑 ∧ 𝜒) → 𝜒) |
ND hypothesis assumption |
simpr 477 |
5 | 5 |
... (𝜓 ∧ 𝜒) |
((𝜑 ∧ 𝜒) → (𝜓 ∧ 𝜒)) |
∧I 2,4 |
jca 554 3,4 |
6 | 6 |
... ((𝜓 ∧ 𝜒) ∨ (𝜓 ∧ 𝜃)) |
((𝜑 ∧ 𝜒) → ((𝜓 ∧ 𝜒) ∨ (𝜓 ∧ 𝜃))) |
∨IR 5 |
orcd 407 5 |
7 | 8 |
...| 𝜃 |
((𝜑 ∧ 𝜃) → 𝜃) |
ND hypothesis assumption |
simpr 477 |
8 | 9 |
... (𝜓 ∧ 𝜃) |
((𝜑 ∧ 𝜃) → (𝜓 ∧ 𝜃)) |
∧I 2,7 |
jca 554 7,8 |
9 | 10 |
... ((𝜓 ∧ 𝜒) ∨ (𝜓 ∧ 𝜃)) |
((𝜑 ∧ 𝜃) → ((𝜓 ∧ 𝜒) ∨ (𝜓 ∧ 𝜃))) |
∨IL 8 |
olcd 408 9 |
10 | 12 |
((𝜓 ∧ 𝜒) ∨ (𝜓 ∧ 𝜃)) |
(𝜑 → ((𝜓 ∧ 𝜒) ∨ (𝜓 ∧ 𝜃))) |
∨E 3,6,9 |
mpjaodan 827 6,10,11 |
The original used Latin letters; we have replaced them with
Greek letters to follow Metamath naming conventions and so that
it is easier to follow the Metamath translation.
The Metamath line-for-line translation of this
natural deduction approach precedes every line with an antecedent
including 𝜑 and uses the Metamath equivalents
of the natural deduction rules.
To add an assumption, the antecedent is modified to include it
(typically by using adantr 481; simpr 477 is useful when you want to
depend directly on the new assumption).
Below is the final metamath proof (which reorders some steps).
A much more efficient proof is ex-natded9.20-2 27275.
(Contributed by David A. Wheeler, 19-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → (𝜓 ∧ (𝜒 ∨ 𝜃))) ⇒ ⊢ (𝜑 → ((𝜓 ∧ 𝜒) ∨ (𝜓 ∧ 𝜃))) |
|
Theorem | ex-natded9.20-2 27275 |
A more efficient proof of Theorem 9.20 of [Clemente] p. 45. Compare
with ex-natded9.20 27274. (Contributed by David A. Wheeler,
19-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → (𝜓 ∧ (𝜒 ∨ 𝜃))) ⇒ ⊢ (𝜑 → ((𝜓 ∧ 𝜒) ∨ (𝜓 ∧ 𝜃))) |
|
Theorem | ex-natded9.26 27276* |
Theorem 9.26 of [Clemente] p. 45, translated line by line using an
interpretation of natural deduction in Metamath. This proof has some
additional complications due to the fact that Metamath's existential
elimination rule does not change bound variables, so we need to verify
that 𝑥 is bound in the conclusion.
For information about ND and Metamath, see the
page on Deduction Form and Natural Deduction
in Metamath Proof Explorer.
The original proof, which uses Fitch style, was written as follows
(the leading "..." shows an embedded ND hypothesis, beginning with
the initial assumption of the ND hypothesis):
# | MPE# | ND Expression |
MPE Translation | ND Rationale |
MPE Rationale |
1 | 3 | ∃𝑥∀𝑦𝜓(𝑥, 𝑦) |
(𝜑 → ∃𝑥∀𝑦𝜓) |
Given |
$e. |
2 | 6 | ...| ∀𝑦𝜓(𝑥, 𝑦) |
((𝜑 ∧ ∀𝑦𝜓) → ∀𝑦𝜓) |
ND hypothesis assumption |
simpr 477. Later statements will have this scope. |
3 | 7;5,4 | ... 𝜓(𝑥, 𝑦) |
((𝜑 ∧ ∀𝑦𝜓) → 𝜓) |
∀E 2,y |
spsbcd 3449 (∀E), 5,6. To use it we need a1i 11 and vex 3203.
This could be immediately done with 19.21bi 2059, but we want to show
the general approach for substitution.
|
4 | 12;8,9,10,11 | ... ∃𝑥𝜓(𝑥, 𝑦) |
((𝜑 ∧ ∀𝑦𝜓) → ∃𝑥𝜓) |
∃I 3,a |
spesbcd 3522 (∃I), 11.
To use it we need sylibr 224, which in turn requires sylib 208 and
two uses of sbcid 3452.
This could be more immediately done using 19.8a 2052, but we want to show
the general approach for substitution.
|
5 | 13;1,2 | ∃𝑥𝜓(𝑥, 𝑦) |
(𝜑 → ∃𝑥𝜓) | ∃E 1,2,4,a |
exlimdd 2088 (∃E), 1,2,3,12.
We'll need supporting
assertions that the variable is free (not bound),
as provided in nfv 1843 and nfe1 2027 (MPE# 1,2) |
6 | 14 | ∀𝑦∃𝑥𝜓(𝑥, 𝑦) |
(𝜑 → ∀𝑦∃𝑥𝜓) |
∀I 5 |
alrimiv 1855 (∀I), 13 |
The original used Latin letters for predicates;
we have replaced them with
Greek letters to follow Metamath naming conventions and so that
it is easier to follow the Metamath translation.
The Metamath line-for-line translation of this
natural deduction approach precedes every line with an antecedent
including 𝜑 and uses the Metamath equivalents
of the natural deduction rules.
Below is the final metamath proof (which reorders some steps).
Note that in the original proof, 𝜓(𝑥, 𝑦) has explicit
parameters. In Metamath, these parameters are always implicit, and the
parameters upon which a wff variable can depend are recorded in the
"allowed substitution hints" below.
A much more efficient proof, using more of Metamath and MPE's
capabilities, is shown in ex-natded9.26-2 27277.
(Contributed by Mario Carneiro, 9-Feb-2017.)
(Revised by David A. Wheeler, 18-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → ∃𝑥∀𝑦𝜓) ⇒ ⊢ (𝜑 → ∀𝑦∃𝑥𝜓) |
|
Theorem | ex-natded9.26-2 27277* |
A more efficient proof of Theorem 9.26 of [Clemente] p. 45. Compare
with ex-natded9.26 27276. (Contributed by Mario Carneiro,
9-Feb-2017.)
(Proof modification is discouraged.) (New usage is discouraged.)
|
⊢ (𝜑 → ∃𝑥∀𝑦𝜓) ⇒ ⊢ (𝜑 → ∀𝑦∃𝑥𝜓) |
|
17.1.4 Definitional examples
|
|
Theorem | ex-or 27278 |
Example for df-or 385. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 9-May-2015.)
|
⊢ (2 = 3 ∨ 4 = 4) |
|
Theorem | ex-an 27279 |
Example for df-an 386. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 9-May-2015.)
|
⊢ (2 = 2 ∧ 3 = 3) |
|
Theorem | ex-dif 27280 |
Example for df-dif 3577. Example by David A. Wheeler. (Contributed
by
Mario Carneiro, 6-May-2015.)
|
⊢ ({1, 3} ∖ {1, 8}) =
{3} |
|
Theorem | ex-un 27281 |
Example for df-un 3579. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 6-May-2015.)
|
⊢ ({1, 3} ∪ {1, 8}) = {1, 3,
8} |
|
Theorem | ex-in 27282 |
Example for df-in 3581. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 6-May-2015.)
|
⊢ ({1, 3} ∩ {1, 8}) = {1} |
|
Theorem | ex-uni 27283 |
Example for df-uni 4437. Example by David A. Wheeler. (Contributed
by
Mario Carneiro, 2-Jul-2016.)
|
⊢ ∪ {{1, 3}, {1,
8}} = {1, 3, 8} |
|
Theorem | ex-ss 27284 |
Example for df-ss 3588. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 6-May-2015.)
|
⊢ {1, 2} ⊆ {1, 2, 3} |
|
Theorem | ex-pss 27285 |
Example for df-pss 3590. Example by David A. Wheeler. (Contributed
by
Mario Carneiro, 6-May-2015.)
|
⊢ {1, 2} ⊊ {1, 2, 3} |
|
Theorem | ex-pw 27286 |
Example for df-pw 4160. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 2-Jul-2016.)
|
⊢ (𝐴 = {3, 5, 7} → 𝒫 𝐴 = (({∅} ∪ {{3}, {5},
{7}}) ∪ ({{3, 5}, {3, 7}, {5, 7}} ∪ {{3, 5, 7}}))) |
|
Theorem | ex-pr 27287 |
Example for df-pr 4180. (Contributed by Mario Carneiro,
7-May-2015.)
|
⊢ (𝐴 ∈ {1, -1} → (𝐴↑2) = 1) |
|
Theorem | ex-br 27288 |
Example for df-br 4654. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 6-May-2015.)
|
⊢ (𝑅 = {〈2, 6〉, 〈3, 9〉}
→ 3𝑅9) |
|
Theorem | ex-opab 27289* |
Example for df-opab 4713. Example by David A. Wheeler. (Contributed
by
Mario Carneiro, 18-Jun-2015.)
|
⊢ (𝑅 = {〈𝑥, 𝑦〉 ∣ (𝑥 ∈ ℂ ∧ 𝑦 ∈ ℂ ∧ (𝑥 + 1) = 𝑦)} → 3𝑅4) |
|
Theorem | ex-eprel 27290 |
Example for df-eprel 5029. Example by David A. Wheeler. (Contributed
by
Mario Carneiro, 18-Jun-2015.)
|
⊢ 5 E {1, 5} |
|
Theorem | ex-id 27291 |
Example for df-id 5024. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 18-Jun-2015.)
|
⊢ (5 I 5 ∧ ¬ 4 I 5) |
|
Theorem | ex-po 27292 |
Example for df-po 5035. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 18-Jun-2015.)
|
⊢ ( < Po ℝ ∧ ¬ ≤ Po
ℝ) |
|
Theorem | ex-xp 27293 |
Example for df-xp 5120. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 7-May-2015.)
|
⊢ ({1, 5} × {2, 7}) = ({〈1,
2〉, 〈1, 7〉} ∪ {〈5, 2〉, 〈5,
7〉}) |
|
Theorem | ex-cnv 27294 |
Example for df-cnv 5122. Example by David A. Wheeler. (Contributed
by
Mario Carneiro, 6-May-2015.)
|
⊢ ◡{〈2, 6〉, 〈3, 9〉} =
{〈6, 2〉, 〈9, 3〉} |
|
Theorem | ex-co 27295 |
Example for df-co 5123. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 7-May-2015.)
|
⊢ ((exp ∘ cos)‘0) =
e |
|
Theorem | ex-dm 27296 |
Example for df-dm 5124. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 7-May-2015.)
|
⊢ (𝐹 = {〈2, 6〉, 〈3, 9〉}
→ dom 𝐹 = {2,
3}) |
|
Theorem | ex-rn 27297 |
Example for df-rn 5125. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 7-May-2015.)
|
⊢ (𝐹 = {〈2, 6〉, 〈3, 9〉}
→ ran 𝐹 = {6,
9}) |
|
Theorem | ex-res 27298 |
Example for df-res 5126. Example by David A. Wheeler. (Contributed
by
Mario Carneiro, 7-May-2015.)
|
⊢ ((𝐹 = {〈2, 6〉, 〈3, 9〉}
∧ 𝐵 = {1, 2}) →
(𝐹 ↾ 𝐵) = {〈2,
6〉}) |
|
Theorem | ex-ima 27299 |
Example for df-ima 5127. Example by David A. Wheeler. (Contributed
by
Mario Carneiro, 7-May-2015.)
|
⊢ ((𝐹 = {〈2, 6〉, 〈3, 9〉}
∧ 𝐵 = {1, 2}) →
(𝐹 “ 𝐵) = {6}) |
|
Theorem | ex-fv 27300 |
Example for df-fv 5896. Example by David A. Wheeler. (Contributed
by Mario
Carneiro, 7-May-2015.)
|
⊢ (𝐹 = {〈2, 6〉, 〈3, 9〉}
→ (𝐹‘3) =
9) |