src/HOL/Datatype.ML

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/Datatype.ML	Thu Aug 19 19:00:42 1999 +0200
@@ -0,0 +1,34 @@
+(*  Title:      HOL/Datatype.ML
+    ID:         $Id$
+    Author:     Stefan Berghofer
+    Copyright   1999  TU Muenchen
+*)
+
+(** sum_case -- the selection operator for sums **)
+
+(*compatibility*)
+val [sum_case_Inl, sum_case_Inr] = sum.cases;
+
+Goal "sum_case (%x::'a. f(Inl x)) (%y::'b. f(Inr y)) s = f(s)";
+by (EVERY1 [res_inst_tac [("s","s")] sumE, 
+            etac ssubst, rtac sum_case_Inl,
+            etac ssubst, rtac sum_case_Inr]);
+qed "surjective_sum";
+
+(*Prevents simplification of f and g: much faster*)
+Goal "s=t ==> sum_case f g s = sum_case f g t";
+by (etac arg_cong 1);
+qed "sum_case_weak_cong";
+
+val [p1,p2] = Goal
+  "[| sum_case f1 f2 = sum_case g1 g2;  \
+\     [| f1 = g1; f2 = g2 |] ==> P |] \
+\  ==> P";
+by (rtac p2 1);
+by (rtac ext 1);
+by (cut_inst_tac [("x","Inl x")] (p1 RS fun_cong) 1);
+by (Asm_full_simp_tac 1);
+by (rtac ext 1);
+by (cut_inst_tac [("x","Inr x")] (p1 RS fun_cong) 1);
+by (Asm_full_simp_tac 1);
+qed "sum_case_inject";