Nuprl - Some Definitions

	Some definitions of interest.

reverse	`Def rev(as) == Case of as; nil nil ; a.as' rev(as') @ [a] (recursive)`

	`Thm* T:Type, as:T List. rev(as) T List`

append	`Def as @ bs == Case of as; nil bs ; a.as' [a / (as' @ bs)] (recursive)`

	`Thm* T:Type, as,bs:T List. (as @ bs) T List`

iff	`Def P Q == (P Q) & (P Q)`

	`Thm* A,B:Prop. (A B) Prop`

l_member	`Def (x l) == i:. i < \|\|l\|\| & x = l[i] T`

	`Thm* T:Type, x:T, l:T List. (x l) Prop`

rev_implies	`Def P Q == Q P`

	`Thm* A,B:Prop. (A B) Prop`

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