allow eval without entering repl

1 files changed, 18 insertions, 5 deletions

diff --git a/bin/Main.hs b/bin/Main.hs
index 2942566..591fc1e 100644
--- a/bin/Main.hs
+++ b/bin/Main.hs
@@ -1,15 +1,21 @@
 module Main where
 
+import           Control.Monad                 (liftM)
+import           Control.Monad.Except          (throwError)
+import           Error                         (LispError (..), LispResult (..),
+                                                unwrap)
 import           Evaluator                     (eval)
 import           Parser                        (Expr (..), parseLispValue)
 import           System.Console.Readline
+import           System.Environment            (getArgs)
 import           Text.ParserCombinators.Parsec
 
-readExpr :: String -> Expr
+readExpr :: String -> LispResult Expr
 readExpr inp =
     case parse parseLispValue "(unknown)" inp of
-      Left err  -> StringLiteral $ show err
-      Right val -> val
+      Left err  -> throwError $ Parse err
+      Right val -> return val
+
 
 repl :: IO ()
 repl = do
@@ -19,8 +25,15 @@ repl = do
       Just ",q" -> return ()
       Just line -> do
           addHistory line
-          print . eval . readExpr $ line
+          -- TODO: don't directly print Either values
+          print $ eval =<< readExpr line
           repl
 
 main :: IO ()
-main = repl
+main = do
+    args <- getArgs
+    if null args
+       then do
+           print ";;; Entering lisk repl ..."
+           repl
+       else print $ eval =<< readExpr (head args)