src/Pure/Syntax/printer.ML

--- a/src/Pure/Syntax/printer.ML	Tue Jul 20 14:41:13 2010 +0200
+++ b/src/Pure/Syntax/printer.ML	Tue Jul 20 14:44:33 2010 +0200
@@ -80,7 +80,7 @@
         Ast.mk_appl (simple_ast_of f) (map simple_ast_of args)
       end
   | simple_ast_of (Bound i) = Ast.Variable ("B." ^ string_of_int i)
-  | simple_ast_of (Abs _) = sys_error "simple_ast_of: Abs";
+  | simple_ast_of (Abs _) = raise Fail "simple_ast_of: Abs";
 
 
 
@@ -246,7 +246,7 @@
       in
         (case xsyms_to_syms xsymbs of
           (symbs, []) => SOME (const, (symbs, nargs symbs, pri))
-        | _ => sys_error "xprod_to_fmt: unbalanced blocks")
+        | _ => raise Fail "Unbalanced pretty-printing blocks")
       end;