assert	Def b == if b True else False fi Thm* b:. b Prop
finite	Def Fin(s) == n:, f:(ns). Bij(n; s; f) Thm* T:Type. Fin(T) Prop
int_seg	Def {i..j} == {k:| i k < j } Thm* m,n:. {m..n} Type
biject	Def Bij(A; B; f) == Inj(A; B; f) & Surj(A; B; f) Thm* A,B:Type, f:(AB). Bij(A; B; f) Prop
nat	Def == {i:| 0i } Thm* Type
lelt	Def i j < k == ij & j < k
surject	Def Surj(A; B; f) == b:B. a:A. f(a) = b Thm* A,B:Type, f:(AB). Surj(A; B; f) 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
le	Def AB == B < A Thm* i,j:. ij Prop
not	Def A == A False Thm* A:Prop. (A) Prop

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