Definition df-bj-1upl 32986

Description: Definition of the Morse monuple (1-tuple). This is not useful per se, but is used as a step towards the definition of couples (2-tuples, or ordered pairs). The reason for "tagging" the set is so that an m-tuple and an n-tuple be equal only when m = n. Note that with this definition, the 0-tuple is the empty set. New usage is discouraged because the precise definition is generally unimportant compared to the characteristic properties bj-2upleq 33000, bj-2uplth 33009, bj-2uplex 33010, and the properties of the projections (see df-bj-pr1 32989 and df-bj-pr2 33003). (Contributed by BJ, 6-Apr-2019.) (New usage is discouraged.)

Assertion

Ref	Expression
df-bj-1upl	|- (| A|) = ( { (/) } X. tag A )

Detailed syntax breakdown of Definition df-bj-1upl

Step	Hyp	Ref	Expression
1		cA	. . 3 class A
2	1	bj-c1upl 32985	. 2 class (| A|)
3		c0 3915	. . . 4 class (/)
4	3	csn 4177	. . 3 class { (/) }
5	1	bj-ctag 32962	. . 3 class tag A
6	4, 5	cxp 5112	. 2 class ( { (/) } X. tag A )
7	2, 6	wceq 1483	1 wff (| A|) = ( { (/) } X. tag A )

This definition is referenced by:  bj-1upleq  32987  bj-pr11val  32993  bj-1uplex  32996  bj-1upln0  32997  bj-pr22val  33007  bj-2upln1upl  33012