exception BadArg;

(* The first argument to demux is P.
   P is a predicate, example
   fun test(x) = x = 4;
   The second argument to demux is a list of arguments for the predicate.
   The third argument to demux is a list of functions. 
   If the predicate is true for a certain argument, the corresponding function is called.
   The fourth argument to demux is the argument to the functions
*) 

fun demux (P, c::cs, f::fs, r) = if P(c) then f(r) else demux (P, cs, fs, r)
|   demux (P, nil, _, r) = raise BadArg
|   demux (P, _, nil, r) = raise BadArg
;
	
(* demux 1 is same as demux, except the fourth argument is a list of arguments for the functions *)
fun demux1 (P, c::cs, f::fs, r::rs) =
	if (P(c)) then f(r) else demux1 (P, cs, fs, rs)
| demux1 (P, nil, _, _) = raise BadArg
| demux1 (P, _, nil, _) = raise BadArg
| demux1 (P, _, _, nil) = raise BadArg
;