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Some definitions of interest.
biject
Def
Bij(A; B; f) == Inj(A; B; f) & Surj(A; B; f)
Thm*
A,B:Type, f:(A
B). Bij(A; B; f)
Prop
compose
Def
(f o g)(x) == f(g(x))
Thm*
A,B,C:Type, f:(B
C), g:(A
B). f o g
A
C
inject
Def
Inj(A; B; f) ==
a1,a2:A. f(a1) = f(a2)
B
a1 = a2
Thm*
A,B:Type, f:(A
B). Inj(A; B; f)
Prop
surject
Def
Surj(A; B; f) ==
b:B.
a:A. f(a) = b
Thm*
A,B:Type, f:(A
B). Surj(A; B; f)
Prop
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