Definition df-fi 6970

Description: Function whose value is the class of finite intersections of the elements of the argument. Note that the empty intersection being the universal class, hence a proper class, it cannot be an element of that class. Therefore, the function value is the class of nonempty finite intersections of elements of the argument (see elfi2 6973). (Contributed by FL, 27-Apr-2008.)

Assertion

Ref	Expression
df-fi	|- fi = ( x e. _V |-> { z | E. y e. ( ~P x i^i Fin ) z = |^| y } )

Distinct variable group:   x, y, z

Detailed syntax breakdown of Definition df-fi

Step	Hyp	Ref	Expression
1		cfi 6969	. 2 class fi
2		vx	. . 3 setvar x
3		cvv 2739	. . 3 class _V
4		vz	. . . . . . 7 setvar z
5	4	cv 1352	. . . . . 6 class z
6		vy	. . . . . . . 8 setvar y
7	6	cv 1352	. . . . . . 7 class y
8	7	cint 3846	. . . . . 6 class |^| y
9	5, 8	wceq 1353	. . . . 5 wff z = |^| y
10	2	cv 1352	. . . . . . 7 class x
11	10	cpw 3577	. . . . . 6 class ~P x
12		cfn 6742	. . . . . 6 class Fin
13	11, 12	cin 3130	. . . . 5 class ( ~P x i^i Fin )
14	9, 6, 13	wrex 2456	. . . 4 wff E. y e. ( ~P x i^i Fin ) z = |^| y
15	14, 4	cab 2163	. . 3 class { z | E. y e. ( ~P x i^i Fin ) z = |^| y }
16	2, 3, 15	cmpt 4066	. 2 class ( x e. _V |-> { z | E. y e. ( ~P x i^i Fin ) z = |^| y } )
17	1, 16	wceq 1353	1 wff fi = ( x e. _V |-> { z | E. y e. ( ~P x i^i Fin ) z = |^| y } )

This definition is referenced by:  fival  6971