--- a/src/HOL/Predicate_Compile_Examples/ROOT.ML Mon Sep 20 09:26:18 2010 +0200
+++ b/src/HOL/Predicate_Compile_Examples/ROOT.ML Mon Sep 20 09:26:19 2010 +0200
@@ -1,2 +1,5 @@
use_thys ["Predicate_Compile_Examples", "Predicate_Compile_Quickcheck_Examples", "Specialisation_Examples", "IMP_1", "IMP_2", "IMP_3", "IMP_4"];
-if getenv "PROLOG_HOME" = "" then () else (use_thys ["Code_Prolog_Examples", "Context_Free_Grammar_Example", "Hotel_Example", "Lambda_Example", "List_Examples"]; setmp_noncritical quick_and_dirty true use_thys ["Reg_Exp_Example"])
+if getenv "EXEC_SWIPL" = "" andalso getenv "EXEC_YAP" = "" then
+ (warning "No prolog system found - could not use example theories that require a prolog system"; ())
+else
+ (use_thys ["Code_Prolog_Examples", "Context_Free_Grammar_Example", "Hotel_Example", "Lambda_Example", "List_Examples"]; setmp_noncritical quick_and_dirty true use_thys ["Reg_Exp_Example"])