Код из лекции

coursework/part1/app/Main.hs

@@ -3,4 +3,4 @@ module Main (main) where
 import Lib
 
 main :: IO ()
-main = someFunc
+main = putStrLn "temp"

coursework/part1/src/Lib.hs

@@ -1,6 +1,50 @@
-module Lib
+{-# LANGUAGE InstanceSigs #-}
-    ( someFunc
-    ) where
 
-someFunc :: IO ()
+module Lib where
-someFunc = putStrLn "someFunc"
+
+import Control.Applicative (Alternative(..))
+import Data.Char (digitToInt, isDigit)
+
+
+newtype Parser tok a =
+    Parser { runParser :: [tok] -> Maybe ([tok], a)}
+
+instance Functor (Parser tok) where
+    fmap :: (a -> b) -> Parser tok a -> Parser tok b
+    fmap g (Parser p) = Parser f where
+        f xs = case p xs of 
+            Nothing -> Nothing
+            Just (cs, c) -> Just (cs, g c)
+
+instance Applicative (Parser tok) where
+    pure :: a -> Parser tok a
+    pure x = Parser $ \toks -> Just (toks, x)
+
+    (<*>) :: Parser tok (a -> b) -> Parser tok a -> Parser tok b
+    Parser u <*> Parser v = Parser f where
+        f xs = case u xs of
+            Nothing -> Nothing
+            Just (xs', g) -> case v xs' of
+                Nothing -> Nothing
+                Just (xs'', x) -> Just (xs'', g x) 
+
+instance Alternative (Parser tok) where
+    empty :: Parser tok a
+    empty = Parser $ \_ -> Nothing
+
+    (<|>) :: Parser tok a -> Parser tok a -> Parser tok a
+    Parser u <|> Parser v = Parser f where
+        f xs = case u xs of
+            Nothing -> v xs
+            z -> z
+
+satisfy :: (tok -> Bool) -> Parser tok tok
+satisfy pr = Parser f where
+    f (c:cs) | pr c = Just (cs, c)
+    f _             = Nothing
+
+char :: Char -> Parser Char Char
+char c = satisfy (== c)
+
+digit :: Parser Char Char
+digit = satisfy isDigit