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@deemp
Created October 2, 2023 13:42
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#lang rzk-1
-- A is contractible there exists x : A such that for any y : A we have x = y.
#def iscontr (A : U) : U
:= ∑ (a : A), (x : A) -> a =_{A} x
-- A is a proposition if for any x, y : A we have x = y
#def isaprop (A : U) : U
:= (x : A) -> (y : A) -> x =_{A} y
-- A is a set if for any x, y : A the type x =_{A} y is a proposition
#def isaset (A : U) : U
:= (x : A) -> (y : A) -> isaprop (x =_{A} y)
-- Non-dependent product of A and B
#def prod (A : U) (B : U) : U
:= ∑ (x : A), B
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