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Metamath Proof Explorer

Theorem funtopon

Description: The class TopOn is a function. (Contributed by BJ, 29-Apr-2021)

Ref Expression
Assertion funtopon 
|- Fun TopOn

Proof

Step Hyp Ref Expression
1 df-topon 
 |-  TopOn = ( y e. _V |-> { x e. Top | y = U. x } )
2 1 funmpt2 
 |-  Fun TopOn