initial commit

Author: Enayaaa

main.hs

@@ -0,0 +1,7 @@
+import System.Environment
+import Debug.Trace
+
+
+main = do
+    args <- getArgs
+    mapM_ putStrLn args

parser.hs

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+{-# LANGUAGE LambdaCase #-}
+module Parser where
+import Control.Monad
+
+-- | empty list of of results denotes failure
+newtype Parser a = Parser {
+                     -- | 
+                     parse :: String -> [(a, String)] }
+
+
+item :: Parser Char
+item = Parser (\case
+                  ""     -> []
+                  (c:cs) -> [(c,cs)])
+
+instance Functor Parser where
+    fmap = liftM
+
+instance Applicative Parser where
+    pure = return
+    (<*>) = ap
+
+instance Monad Parser where
+    return a = Parser (\cs -> [(a,cs)])
+    p >>= f  = Parser (\cs -> concat [parse (f a) cs' | (a,cs') <- parse p cs])
+
+-- | consume three chars, throw away 2nd and return tuple of 1st and 3rd char
+p :: Parser (Char,Char)
+p  = do { c <- item; item; d <- item; return (c,d); }