Nuprl - Some Definitions

	Some definitions of interest.

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`

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

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

sublist	`Def L1 L2 == f:(\|\|L1\|\|\|\|L2\|\|). increasing(f;\|\|L1\|\|) & (j:\|\|L1\|\|. L1[j] = L2[(f(j))] T)`

	`Thm* T:Type, L1,L2:T List. L1 L2 Prop`

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