Some definitions of interest.
compose_iter	Def  f{i}(x) == if i=0 x else f(f{i-1}(x)) fi  (recursive)
	Thm*  f:(AA), i:. f{i}  AA
nat	Def   == {i:| 0i }
	Thm*    Type
nat_plus	Def   == {i:| 0<i }
	Thm*    Type

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