diff -r 000000000000 -r 7949f97df77a Subst/uterm.thy
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Subst/uterm.thy	Thu Sep 16 12:21:07 1993 +0200
@@ -0,0 +1,58 @@
+(*  Title: 	Substitutions/uterm.thy
+    Author: 	Martin Coen, Cambridge University Computer Laboratory
+    Copyright   1993  University of Cambridge
+
+Simple term structure for unifiation.
+Binary trees with leaves that are constants or variables.
+*)
+
+UTerm = Sexp +
+
+types uterm 1
+
+arities 
+  uterm     :: (term)term
+
+consts
+  UTerm     :: "'a node set set => 'a node set set"
+  Rep_UTerm :: "'a uterm => 'a node set"
+  Abs_UTerm :: "'a node set => 'a uterm"
+  VAR       :: "'a node set => 'a node set"
+  CONST     :: "'a node set => 'a node set"
+  COMB      :: "['a node set, 'a node set] => 'a node set"
+  Var       :: "'a => 'a uterm"
+  Const     :: "'a => 'a uterm"
+  Comb      :: "['a uterm, 'a uterm] => 'a uterm"
+  UTerm_rec :: "['a node set, 'a node set => 'b, 'a node set => 'b, \
+\                ['a node set , 'a node set, 'b, 'b]=>'b] => 'b"
+  uterm_rec :: "['a uterm, 'a => 'b, 'a => 'b, \
+\                ['a uterm, 'a uterm,'b,'b]=>'b] => 'b"
+
+rules
+  UTerm_def	"UTerm(A) == lfp(%Z. A <+> A <+> Z <*> Z)"
+    (*faking a type definition...*)
+  Rep_UTerm 		"Rep_UTerm(xs): UTerm(range(Leaf))"
+  Rep_UTerm_inverse 	"Abs_UTerm(Rep_UTerm(xs)) = xs"
+  Abs_UTerm_inverse 	"M: UTerm(range(Leaf)) ==> Rep_UTerm(Abs_UTerm(M)) = M"
+     (*defining the concrete constructors*)
+  VAR_def  	"VAR(v) == In0(v)"
+  CONST_def  	"CONST(v) == In1(In0(v))"
+  COMB_def 	"COMB(t,u) == In1(In1(t . u))"
+     (*defining the abstract constructors*)
+  Var_def  	"Var(v) == Abs_UTerm(VAR(Leaf(v)))"
+  Const_def  	"Const(c) == Abs_UTerm(CONST(Leaf(c)))"
+  Comb_def 	"Comb(t,u) == Abs_UTerm(COMB(Rep_UTerm(t),Rep_UTerm(u)))"
+
+     (*uterm recursion*)
+  UTerm_rec_def	
+   "UTerm_rec(M,b,c,d) == wfrec(trancl(pred_Sexp), M, \
+\          %z g. Case(z, %x. b(x), \
+\                        %w. Case(w, %x. c(x), \
+\                                 %v. Split(v, %x y. d(x,y,g(x),g(y))))))"
+
+  uterm_rec_def
+   "uterm_rec(t,b,c,d) == \
+\   UTerm_rec(Rep_UTerm(t), %x.b(Inv(Leaf,x)), %x.c(Inv(Leaf,x)), \
+\                           %x y q r.d(Abs_UTerm(x),Abs_UTerm(y),q,r))"
+
+end