use std pkg iter =	type enumiter(@a) = struct		idx	: std.size		sl	: @a[:]	;; 	impl iterable enumiter(@a) -> (std.size, @a)	generic byenum	: (a : @a[:] -> enumiter(@a));; generic byenum = {a	-> [.sl = a, .idx = 0]} impl iterable enumiter(@a) -> (std.size, @a) =	__iternext__ = {itp, valp		if itp.idx == itp.sl.len			-> false		;;		valp# = (itp.idx, itp.sl[itp.idx])		itp.idx++		-> true	} 	__iterfin__ = {itp, valp	};;