| | 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 |
|
| decidable | Def Dec(P) == P   P |
| | | Thm* A:Prop. Dec(A) Prop |
|
| inject | Def Inj(A; B; f) == a1,a2:A. f(a1) = f(a2) B   a1 = a2 |
| | | Thm* A,B:Type, f:(AB). Inj(A; B; f) Prop |
|
| pi1 | Def 1of(t) == t.1 |
| | | Thm* A:Type, B:(AType), p:(a:A B(a)). 1of(p) A |
|
| pi2 | Def 2of(t) == t.2 |
| | | Thm* A:Type, B:(AType), p:(a:AB(a)). 2of(p) B(1of(p)) |
|
| surject | Def Surj(A; B; f) == b:B.  a:A. f(a) = b |
| | | Thm* A,B:Type, f:(AB). Surj(A; B; f) Prop |
