Move transfer into the GF repo.

src/Transfer/InterpreterAPI.hs

@@ -0,0 +1,31 @@
+module Transfer.InterpreterAPI (Env, load, loadFile, evaluateString) 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.
+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