Definition df-finxp 33221

Description: Define Cartesian exponentiation on a class.

Note that this definition is limited to finite exponents, since it is defined using nested ordered pairs. If tuples of infinite length are needed, or if they might be needed in the future, use df-ixp 7909 or df-map 7859 instead. The main advantage of this definition is that it integrates better with functions and relations. For example if R is a subset of ( A ^^ ^^ 2o ), then df-br 4654 can be used on it, and df-fv 5896 can also be used, and so on.

It's also worth keeping in mind that ( ( U ^^ ^^ M ) X. ( U ^^ ^^ N ) ) is generally not equal to ( U ^^ ^^ ( M +o N ) ).

This definition is technical. Use finxp1o 33229 and finxpsuc 33235 for a more standard recursive experience. (Contributed by ML, 16-Oct-2020.)

Assertion

Ref	Expression
df-finxp	|- ( U ^^ ^^ N ) = { y | ( N e. om /\ (/) = ( rec ( ( n e. om , x e. _V |-> if ( ( n = 1o /\ x e. U ) , (/) , if ( x e. ( _V X. U ) , <. U. n , ( 1st ` x ) >. , <. n , x >. ) ) ) , <. N , y >. ) ` N ) ) }

Distinct variable groups:   U, n, x, y   n, N, x, y

Detailed syntax breakdown of Definition df-finxp

Step	Hyp	Ref	Expression
1		cU	. . 3 class U
2		cN	. . 3 class N
3	1, 2	cfinxp 33220	. 2 class ( U ^^ ^^ N )
4		com 7065	. . . . 5 class om
5	2, 4	wcel 1990	. . . 4 wff N e. om
6		c0 3915	. . . . 5 class (/)
7		vn	. . . . . . . 8 setvar n
8		vx	. . . . . . . 8 setvar x
9		cvv 3200	. . . . . . . 8 class _V
10	7	cv 1482	. . . . . . . . . . 11 class n
11		c1o 7553	. . . . . . . . . . 11 class 1o
12	10, 11	wceq 1483	. . . . . . . . . 10 wff n = 1o
13	8	cv 1482	. . . . . . . . . . 11 class x
14	13, 1	wcel 1990	. . . . . . . . . 10 wff x e. U
15	12, 14	wa 384	. . . . . . . . 9 wff ( n = 1o /\ x e. U )
16	9, 1	cxp 5112	. . . . . . . . . . 11 class ( _V X. U )
17	13, 16	wcel 1990	. . . . . . . . . 10 wff x e. ( _V X. U )
18	10	cuni 4436	. . . . . . . . . . 11 class U. n
19		c1st 7166	. . . . . . . . . . . 12 class 1st
20	13, 19	cfv 5888	. . . . . . . . . . 11 class ( 1st ` x )
21	18, 20	cop 4183	. . . . . . . . . 10 class <. U. n , ( 1st ` x ) >.
22	10, 13	cop 4183	. . . . . . . . . 10 class <. n , x >.
23	17, 21, 22	cif 4086	. . . . . . . . 9 class if ( x e. ( _V X. U ) , <. U. n , ( 1st ` x ) >. , <. n , x >. )
24	15, 6, 23	cif 4086	. . . . . . . 8 class if ( ( n = 1o /\ x e. U ) , (/) , if ( x e. ( _V X. U ) , <. U. n , ( 1st ` x ) >. , <. n , x >. ) )
25	7, 8, 4, 9, 24	cmpt2 6652	. . . . . . 7 class ( n e. om , x e. _V |-> if ( ( n = 1o /\ x e. U ) , (/) , if ( x e. ( _V X. U ) , <. U. n , ( 1st ` x ) >. , <. n , x >. ) ) )
26		vy	. . . . . . . . 9 setvar y
27	26	cv 1482	. . . . . . . 8 class y
28	2, 27	cop 4183	. . . . . . 7 class <. N , y >.
29	25, 28	crdg 7505	. . . . . 6 class rec ( ( n e. om , x e. _V |-> if ( ( n = 1o /\ x e. U ) , (/) , if ( x e. ( _V X. U ) , <. U. n , ( 1st ` x ) >. , <. n , x >. ) ) ) , <. N , y >. )
30	2, 29	cfv 5888	. . . . 5 class ( rec ( ( n e. om , x e. _V |-> if ( ( n = 1o /\ x e. U ) , (/) , if ( x e. ( _V X. U ) , <. U. n , ( 1st ` x ) >. , <. n , x >. ) ) ) , <. N , y >. ) ` N )
31	6, 30	wceq 1483	. . . 4 wff (/) = ( rec ( ( n e. om , x e. _V |-> if ( ( n = 1o /\ x e. U ) , (/) , if ( x e. ( _V X. U ) , <. U. n , ( 1st ` x ) >. , <. n , x >. ) ) ) , <. N , y >. ) ` N )
32	5, 31	wa 384	. . 3 wff ( N e. om /\ (/) = ( rec ( ( n e. om , x e. _V |-> if ( ( n = 1o /\ x e. U ) , (/) , if ( x e. ( _V X. U ) , <. U. n , ( 1st ` x ) >. , <. n , x >. ) ) ) , <. N , y >. ) ` N ) )
33	32, 26	cab 2608	. 2 class { y | ( N e. om /\ (/) = ( rec ( ( n e. om , x e. _V |-> if ( ( n = 1o /\ x e. U ) , (/) , if ( x e. ( _V X. U ) , <. U. n , ( 1st ` x ) >. , <. n , x >. ) ) ) , <. N , y >. ) ` N ) ) }
34	3, 33	wceq 1483	1 wff ( U ^^ ^^ N ) = { y | ( N e. om /\ (/) = ( rec ( ( n e. om , x e. _V |-> if ( ( n = 1o /\ x e. U ) , (/) , if ( x e. ( _V X. U ) , <. U. n , ( 1st ` x ) >. , <. n , x >. ) ) ) , <. N , y >. ) ` N ) ) }

This definition is referenced by:  dffinxpf  33222  finxpeq1  33223  finxpeq2  33224  csbfinxpg  33225  finxp0  33228  finxp1o  33229  finxpnom  33238