src/HOL/MiniML/W.thy

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/MiniML/W.thy	Wed Oct 25 09:46:46 1995 +0100
@@ -0,0 +1,28 @@
+(* Title:     HOL/MiniML/W.thy
+   ID:        $Id$
+   Author:    Dieter Nazareth and Tobias Nipkow
+   Copyright  1995 TU Muenchen
+
+Type inference algorithm W
+*)
+
+W = MiniML + 
+
+types 
+        result_W = "(subst * type_expr * nat)maybe"
+
+(* type inference algorithm W *)
+consts
+	W :: "[expr, type_expr list, nat] => result_W"
+
+primrec W expr
+  W_Var	"W (Var i) a n = (if i < length a then Ok(id_subst, nth i a, n)
+		          else Fail)"
+  W_Abs	"W (Abs e) a n = W e ((TVar n)#a) (Suc n)    bind   
+		         (%(s,t,m). Ok(s, Fun (s n) t, m) )"
+  W_App	"W (App e1 e2) a n =
+ 		 W e1 a n    bind
+		 (%(s1,t1,m1). W e2 ($ s1 a) m1   bind   
+		 (%(s2,t2,m2). mgu ($ s2 t1) (Fun t2 (TVar m2)) bind
+		 (%u. Ok( ($ u) o (($ s2) o s1), $ u (TVar m2), Suc m2) )))"
+end