(*---------------------------------------------------------------------------------///*)
        | ListP ps => case ex of
            List xs => case (xs, ps) of
                (h::nil, g::nil) => match(h, g)
                | (h::t, g::r) => case match(h,g) of
                    SOME v => SOME (v @ (case match(List t, ListP r) of
                        SOME a => a
                        ))
                    | NONE => NONE

(*--------------------------------------PAIR-------------------------------------------///
        | PairP([a1, a2]) => case ex of
            Pair([b1,b2]) => if(match(b2, a2) = NONE orelse match(b1, a1) = NONE) then NONE else SOME (Option.valOf(match(b1, a1)) @ Option.valOf(match(b2, a2))) *)

(*ERROR*)
D:\FRI\FP\Seminar\seminar.sml:72.35-81.162 Error: types of rules don't agree [tycon mismatch]
  earlier rule(s): ''Z list option -> ''Z list option
  this rule: pattern -> ''Z list option
  in rule:
    PairP (a1 :: a2 :: nil) =>
      (case ex
        of Pair (b1 :: b2 :: nil) =>
             if (match (b2,a2) = NONE) orelse (match (b1,a1) = NONE)
             then NONE
             else SOME
                    (Option.valOf (match (b1,a1)) @
                       Option.valOf (match (b2,a2))))