(* Title: MiniML.thy
Author: Thomas Stauner
Copyright 1995 TU Muenchen
Recursive definition of type inference algorithm I for Mini_ML.
*)
I = W +
consts
I :: [expr, typ list, nat, subst] => result_W
primrec I expr
I_Var "I (Var i) a n s = (if i < length a then Ok(s, nth i a, n)
else Fail)"
I_Abs "I (Abs e) a n s = ( (s,t,m) := I e ((TVar n)#a) (Suc n) s;
Ok(s, TVar n -> t, m) )"
I_App "I (App e1 e2) a n s =
( (s1,t1,m1) := I e1 a n s;
(s2,t2,m2) := I e2 a m1 s1;
u := mgu ($s2 t1) ($s2 t2 -> TVar m2);
Ok($u o s2, TVar m2, Suc m2) )"
end