diff --git a/src/Main.purs b/src/Main.purs new file mode 100644 index 0000000..f52c585 --- /dev/null +++ b/src/Main.purs @@ -0,0 +1,103 @@ +module Main where + +import Prelude +import Effect (Effect) +import Effect.Console (log) + +import Data.Maybe (Maybe(..)) +import Data.Tuple (Tuple(..)) +import Data.String.CodeUnits (uncons) + +newtype Parser v = Parser (String -> Maybe (Tuple v String)) +parse :: forall a. Parser a -> (String -> Maybe (Tuple a String)) +parse (Parser p) = p + +itemP :: Parser Char +itemP = Parser p + where p str = case uncons str of + Nothing -> Nothing + Just { head: x, tail: xs } -> Just (Tuple x xs) + +instance functorParser :: Functor Parser where + map f (Parser p) = + Parser $ \s0 -> do + (Tuple x s1) <- p s0 + pure (Tuple (f x) s1) + +instance applyParser :: Apply Parser where + apply (Parser p1) (Parser p2) + = Parser $ \str -> case p1 str of + Nothing -> Nothing + Just (Tuple x1 xs1) -> case p2 xs1 of + Nothing -> Nothing + Just (Tuple x2 xs2) -> Just (Tuple (x1 x2) xs2) + +instance applicativeParser :: Applicative Parser where + pure a = Parser $ \str -> Just (Tuple a str) + +instance bindParser :: Bind Parser where + bind (Parser p) f = Parser $ \str -> case p str of + Nothing -> Nothing + Just (Tuple x xs) -> + let (Parser p2) = f x + in p2 xs + +isf :: Parser Boolean +isf = (_ == 'f') <$> itemP + +isf2 :: Parser Boolean +isf2 = (==) <$> itemP <*> pure 'f' + +ishi :: Parser (Tuple Boolean Boolean) +ishi = Tuple <$> ((_ == 'h') <$> itemP) <*> ((_ == 'i') <$> itemP) + +ishi2 :: Parser (Tuple Boolean Boolean) +ishi2 = ado + h <- itemP + i <- itemP + in Tuple (h == 'h') (i == 'i') + +isffound :: Maybe (Tuple Boolean String) -> Effect Unit +isffound maybe = case maybe of + Nothing -> log "no more data" + Just (Tuple b str) -> do + let toprint = if b then "FOUND IT" else "not found" + log $ toprint <> ", rest: " <> str + +main :: Effect Unit +main = do + log "🍝" + + case parse ishi2 "hi" of + Just (Tuple x y) -> log ("parsing 'hi': " <> show x <> " " <> show y) + Nothing -> log "coudn't parse two letters" + + case parse ishi2 "no" of + Just (Tuple x y) -> log ("parsing 'no': " <> show x <> " " <> show y) + Nothing -> log "coudn't parse two letters" + + case parse ishi2 "ho" of + Just (Tuple x y) -> log ("parsing 'ho': " <> show x <> " " <> show y) + Nothing -> log "coudn't parse two letters" + + case parse ishi2 "ni" of + Just (Tuple x y) -> log ("parsing 'ni': " <> show x <> " " <> show y) + Nothing -> log "coudn't parse two letters" + + case parse ishi2 "" of + Just (Tuple x y) -> log ("parsing '': " <> show x <> " " <> show y) + Nothing -> log "coudn't parse two letters" + + +-- JUST WORKS +-- isffound $ parse isf "fable" +-- isffound $ parse isf "f" +-- isffound $ parse isf "n" +-- isffound $ parse isf "" +-- +-- isffound $ parse isf2 "fable" +-- isffound $ parse isf2 "f" +-- isffound $ parse isf2 "n" +-- isffound $ parse isf2 "" + + log "end"