[added support for an error function which terminates the program with a user-supplied error message
mail@stefanwehr.de**20051001130733] {
hunk ./Phrac/Interpreter.hs 34
-import Phrac.UniqIdents ( builtinDataId, isMain )
+import Phrac.UniqIdents ( builtinDataId, isMain, isError, mkValId )
hunk ./Phrac/Interpreter.hs 148
-       let v = lookupEnv x env
-       return v
+       if isError x
+          then let arg = mkValId "__ error argument __" (-1)
+                   in return $ ClosVal $ Closure emptyEnv [PVar arg] (UserError arg)
+          else let v = lookupEnv x env
+                   in return v
hunk ./Phrac/Interpreter.hs 308
+
+eval env (UserError x) = 
+    do val <- evalStrict env (Var x)
+       let s = printStringList val
+       panic ("User error: " ++ s)
hunk ./Phrac/ParseSyntax.hs 416
-
+    | UserError ValId             -- used to implement the `error' function.
+                                  -- the ValId is the identifier to which to
+                                  -- error message is bound.
hunk ./Phrac/UniqIdents.hs 28
-  isMain,
+  isMain, isError,
hunk ./Phrac/UniqIdents.hs 124
+isError (ValId (Id _ s)) = s == "error"
hunk ./PhracPrelude.phc 70
+error :: List Char -> __a;
+error = error;
+
hunk ./PhracPrelude.phc 74
-undefined = undefined;
+undefined = error "undefined";
}