diff -r 000000000000 -r a5a9c433f639 src/CTT/ex/typechk.ML
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/CTT/ex/typechk.ML	Thu Sep 16 12:20:38 1993 +0200
@@ -0,0 +1,82 @@
+(*  Title: 	CTT/ex/typechk
+    ID:         $Id$
+    Author: 	Lawrence C Paulson, Cambridge University Computer Laboratory
+    Copyright   1991  University of Cambridge
+  
+Easy examples: type checking and type deduction
+*)
+
+writeln"Single-step proofs: verifying that a type is well-formed";
+
+goal CTT.thy "?A type";
+by (resolve_tac form_rls 1);
+result(); 
+writeln"getting a second solution";
+back();
+by (resolve_tac form_rls 1);
+by (resolve_tac form_rls 1);
+result(); 
+
+goal CTT.thy "PROD z:?A . N + ?B(z) type";
+by (resolve_tac form_rls 1);
+by (resolve_tac form_rls 1);
+by (resolve_tac form_rls 1);
+by (resolve_tac form_rls 1);
+by (resolve_tac form_rls 1);
+uresult(); 
+
+
+writeln"Multi-step proofs: Type inference";
+
+goal CTT.thy "PROD w:N. N + N type";
+by form_tac;
+result(); 
+
+goal CTT.thy "<0, succ(0)> : ?A";
+by (intr_tac[]);
+result(); 
+
+goal CTT.thy "PROD w:N . Eq(?A,w,w) type";
+by (typechk_tac[]);
+result(); 
+
+goal CTT.thy "PROD x:N . PROD y:N . Eq(?A,x,y) type";
+by (typechk_tac[]);
+result(); 
+
+writeln"typechecking an application of fst";
+goal CTT.thy "(lam u. split(u, %v w.v)) ` <0, succ(0)> : ?A";
+by (typechk_tac[]);
+result(); 
+
+writeln"typechecking the predecessor function";
+goal CTT.thy "lam n. rec(n, 0, %x y.x) : ?A";
+by (typechk_tac[]);
+result(); 
+
+writeln"typechecking the addition function";
+goal CTT.thy "lam n. lam m. rec(n, m, %x y.succ(y)) : ?A";
+by (typechk_tac[]);
+result(); 
+
+(*Proofs involving arbitrary types.
+  For concreteness, every type variable left over is forced to be N*)
+val N_tac = TRYALL (rtac NF);
+
+goal CTT.thy "lam w. <w,w> : ?A";
+by (typechk_tac[]);
+by N_tac;
+result(); 
+
+goal CTT.thy "lam x. lam y. x : ?A";
+by (typechk_tac[]);
+by N_tac;
+result(); 
+
+writeln"typechecking fst (as a function object) ";
+goal CTT.thy "lam i. split(i, %j k.j) : ?A";
+by (typechk_tac[]);
+by N_tac;
+result(); 
+
+writeln"Reached end of file.";