Definitions | b, t T, , Unit, int_seg(i; j), A, x:A. B(x), P Q, x:A. B(x), P   Q, priority-select(f; g; as), , tl(l), i <z j,  b, i z j, if b then t else f fi , Y, nth_tl(n;as), hd(l), l[i], A B, lelt(i; j; k), ff, prop{i:l}, P  Q, False, tt, ||as||, P  Q, P Q, decidable(P),  x. t(x), isl(x), list_accum(x,a.f(x;a); y; l), ge(i; j), True, guard(T), sq_type(T),  x,y. t(x;y), T |