Tail recursing main function

[my-scheme.git] / app / Main.hs

diff --git a/app/Main.hs b/app/Main.hs
index 6fcf6675f175374d22b749097dc06142312b8400..233fa6c9e85a81dfb98934e6624baa1391a14489 100644 (file)
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -1,4 +1,5 @@
 module Main where
+import Control.Monad
 import Text.ParserCombinators.Parsec hiding (spaces)
 import System.Environment
 
@@ -8,6 +9,7 @@ data LispVal = Atom String
              | Number Integer
              | String String
              | Bool Bool
+             deriving Show
 
 symbol :: Parser Char
 symbol = oneOf "!#$%&|*+-/:<=>?@^_~"
@@ -32,12 +34,23 @@ parseAtom = do
                 "#f" -> Bool False
                 _    -> Atom atom
 
+parseNumber :: Parser LispVal
+parseNumber = do ds <- many1 digit
+                 let a = read ds
+                 return $ Number a
+
+parseExpr :: Parser LispVal
+parseExpr = parseString
+        <|> parseAtom
+        <|> parseNumber
+
 readExpr :: String -> String
-readExpr input = case parse (spaces >> symbol) "lisp" input of
+readExpr input = case parse parseExpr "lisp" input of
     Left err -> "No match: " ++ show err
-    Right val -> "Found value"
+    Right val -> "Found value: " ++ show val
 
 main :: IO ()
 main = do
     args <- getLine
     putStrLn (readExpr args)
+    main