Metamath Proof Explorer


Definition df-res

Description: Define the restriction of a class. Definition 6.6(1) of TakeutiZaring p. 24. For example, the expression ` ( exp |`RR ) (used in reeff1 ) means "the exponential function e to the x, but the exponent x must be in the reals" ( df-ef defines the exponential function, which normally allows the exponent to be a complex number). Another example is ( F = { <. 2 , 6 >. , <. 3 , 9 >. } /\ B = { 1 , 2 } ) -> ` ( F |`B ) = { <. 2 , 6 >. } ( ex-res ). We do not introduce a special syntax for the corestriction of a class: it will be expressed either as the intersection ( A i^i ( _V X. B ) ) or as the converse of the restricted converse (see cnvrescnv ). (Contributed by NM, 2-Aug-1994)

Ref Expression
Assertion df-res ( 𝐴𝐵 ) = ( 𝐴 ∩ ( 𝐵 × V ) )

Detailed syntax breakdown

Step Hyp Ref Expression
0 cA 𝐴
1 cB 𝐵
2 0 1 cres ( 𝐴𝐵 )
3 cvv V
4 1 3 cxp ( 𝐵 × V )
5 0 4 cin ( 𝐴 ∩ ( 𝐵 × V ) )
6 2 5 wceq ( 𝐴𝐵 ) = ( 𝐴 ∩ ( 𝐵 × V ) )