GF/src is now for 2.9, and the new sources are in src-3.0 - keep it this way until the release of GF 3

src-3.0/Transfer/InterpreterAPI.hs

@@ -0,0 +1,39 @@
+module Transfer.InterpreterAPI (Env, builtin,
+                                load, loadFile, 
+                                evaluateString, evaluateExp
+                               ) where
+
+import Transfer.Core.Abs
+import Transfer.Core.Lex
+import Transfer.Core.Par
+import Transfer.Core.Print
+import Transfer.Interpreter
+import Transfer.ErrM
+
+-- | Read a transfer module in core format from a string.
+load :: Monad m => 
+        String -- ^ Input source name, for error messages.
+     -> String -- ^ Module contents.
+     -> m Env
+load n s = case pModule (myLexer s) of
+              Bad e -> fail $ "Parse error in " ++ n ++ ": " ++ e
+              Ok  m -> return $ addModuleEnv builtin m
+
+-- | Read a transfer module in core format from a file.
+--   Fails in the IO monad if there is a problem loading the file.
+loadFile :: FilePath -> IO Env
+loadFile f = readFile f >>= load f
+
+-- | Read a transfer expression from a string and evaluate it.
+--   Returns the result as a string.
+evaluateString :: Monad m => Env -> String -> m String
+evaluateString env s = 
+    case pExp (myLexer s) of
+        Bad e -> fail $ "Parse error: " ++ e
+        Ok  e -> do
+                 let v = eval env e
+                 return $ printValue v
+
+-- | Evaluate an expression in the given environment.
+evaluateExp :: Env -> Exp -> Exp
+evaluateExp env exp = valueToExp $ eval env exp