Using nested pattern matching (ML)

	fun zip3 list_triple =
	case list_triple of
	([],[],[]) => []
	|(hd1:tl1, hd2:tl2, hd3:tl3) => (hd1,hd2,hd3) :: zip3 (tl1,tl2,tl3)
	| _ => raise ListLengthMismatch
	fun unzip lst =
	case lst of
	[] => ([],[],[])
	|(a,b,c)::tl => let val (l1,l2,l3) = unzip tl
	in
	(a::l1, b::l2, c::l3)
	end
	fun nondecreasing xs = (* int list -> bool *)
	case xs of
	[] => true
	| _::[] => true
	| head::(neck::rest) => head <= neck andalso nondecreasing (neck::rest)
	datatype sign = Positive | Negative | Zero
	fun multsign (x1, x2) = (* int * int -> sign *)
	let fun sgn x = if x = 0 then Zero else if x > 0 then Positive else Negative
	in
	case (sgn x, sgn y) of
	(Positive, Positive) => Positive
	| (Negative, Negative) => Positive
	| (Zero, _) => Zero
	| (_, Zero) => Zero
	| _ => Negative
	end

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