Tail recursing main function

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

diff --git a/app/Main.hs b/app/Main.hs
index 7c987cee50d96d97e445cc1b18756f845a47a24f..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 "!#$%&|*+-/:<=>?@^_~"
@@ -26,14 +28,29 @@ parseAtom :: Parser LispVal
 parseAtom = do
     a <- letter <|> symbol
     b <- many (letter <|> digit <|> symbol)
-    return $ Atom (a:b)
+    let atom = a:b
+    return $ case atom of
+                "#t" -> Bool True
+                "#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