diff --git a/src/Transfer/CompilerAPI.hs b/src/Transfer/CompilerAPI.hs
new file mode 100644
index 000000000..e1ef32f62
--- /dev/null
+++ b/src/Transfer/CompilerAPI.hs
@@ -0,0 +1,72 @@
+module Transfer.CompilerAPI where
+
+import Transfer.Syntax.Lex
+import Transfer.Syntax.Par
+import Transfer.Syntax.Print
+import Transfer.Syntax.Abs
+import Transfer.Syntax.Layout
+
+import Transfer.ErrM
+import Transfer.SyntaxToCore
+
+import Transfer.PathUtil
+
+import System.Directory
+
+
+-- | Compile a source module file to a a code file.
+compileFile :: [FilePath]  -- ^ directories to look for imported modules in
+            -> FilePath    -- ^ source module file
+            -> IO FilePath -- ^ path to the core file that was written
+compileFile path f = do
+                     ds <- loadModule path f
+                     s <- compile ds
+                     writeFile coreFile s
+                     return coreFile
+  where coreFile = replaceFilenameSuffix f "trc"
+
+-- | Compile a self-contained list of declarations to a core program.
+compile :: Monad m => [Decl] -> m String
+compile m = return (printTree $ declsToCore m)
+
+-- | Load a source module file and all its dependencies.
+loadModule :: [FilePath] -- ^ directories to look for imported modules in
+           -> FilePath   -- ^ source module file
+           -> IO [Decl]
+loadModule path f = 
+    do
+    s <- readFile f
+    Module is ds <- case pModule (myLLexer s) of
+                     Bad e    -> fail $ "Parse error in " ++ f ++ ": " ++ e
+                     Ok  m    -> return m 
+    let deps = [ i | Import (Ident i) <- is ]
+    let path' = directoryOf f : path
+    files <- mapM (findFile path' . (++".tr")) deps
+    dss <- mapM (loadModule path) files
+    return $ concat (dss++[ds])
+
+myLLexer :: String -> [Token]
+myLLexer = resolveLayout True . myLexer
+
+-- | Find a file in one of the given directories.
+--   Fails if the file was not found.
+findFile :: [FilePath] -- ^ directories to look in
+          -> FilePath   -- ^ file name to find
+          -> IO FilePath
+findFile path f = 
+    do
+    mf <- findFileM path f
+    case mf of
+        Nothing -> fail $ f ++ " not found in path: " ++ show path
+        Just f' -> return f'
+
+-- | Find a file in one of the given directories.             
+findFileM :: [FilePath] -- ^ directories to look in
+          -> FilePath   -- ^ file name to find
+          -> IO (Maybe FilePath)
+findFileM []     _ = return Nothing
+findFileM (p:ps) f = 
+    do
+    let f' = p ++ "/" ++ f
+    e <- doesFileExist f'
+    if e then return (Just f') else findFileM ps f
diff --git a/transfer/compile_to_core.hs b/transfer/compile_to_core.hs
index 1f9ea746b..b35d906d0 100644
--- a/transfer/compile_to_core.hs
+++ b/transfer/compile_to_core.hs
@@ -1,52 +1,25 @@
 module Main where
 
-import Transfer.Syntax.Lex
-import Transfer.Syntax.Par
-import Transfer.Syntax.Print
-import Transfer.Syntax.Abs
-import Transfer.Syntax.Layout
-
-import Transfer.ErrM
-import Transfer.SyntaxToCore
-
-import Transfer.PathUtil
+import Transfer.CompilerAPI
 
+import Data.List (partition, isPrefixOf)
 import System.Environment
 import System.Exit
 import System.IO
 
-import Debug.Trace
-
-myLLexer = resolveLayout True . myLexer
-
-compile :: Monad m => [Decl] -> m String
-compile m = return (printTree $ declsToCore m)
-
-loadModule :: FilePath -> IO [Decl]
-loadModule f = 
-    do
-    s <- readFile f
-    Module is ds <- case pModule (myLLexer s) of
-                     Bad e    -> die $ "Parse error in " ++ f ++ ": " ++ e
-                     Ok  m    -> return m 
-    let dir = directoryOf f
-        deps = [ replaceFilename f i ++ ".tr" | Import (Ident i) <- is ]
-    dss <- mapM loadModule deps
-    return $ concat (ds:dss)
-
 die :: String -> IO a
 die s = do
         hPutStrLn stderr s
         exitFailure
 
-coreFile :: FilePath -> FilePath
-coreFile f = replaceFilenameSuffix f "trc"
-
-compileFile :: FilePath -> IO String
-compileFile f = loadModule f >>= compile
-
 main :: IO ()
-main = do args <- getArgs
-          case args of
-            [f] -> compileFile f >>= writeFile (coreFile f)
-            _   -> die "Usage: compile_to_core <file>"
+main = do 
+       args <- getArgs
+       let (flags,files) = partition ("-" `isPrefixOf`) args
+           path = [ p | ('-':'i':p) <- flags ]
+       case files of
+         [f] -> do
+                cf <- compileFile path f
+                putStrLn $ "Wrote " ++ cf
+                return ()
+         _   -> die "Usage: compile_to_core [-i<path> [-i<path> ... ]] <file>"