diff options
Diffstat (limited to 'src/parser.hs')
| -rw-r--r-- | src/parser.hs | 34 |
1 files changed, 21 insertions, 13 deletions
diff --git a/src/parser.hs b/src/parser.hs index 49d23d7..6c2b8af 100644 --- a/src/parser.hs +++ b/src/parser.hs @@ -1,4 +1,7 @@ -module Parser where +module Parser +( parse +, equationP +) where import Control.Applicative import Control.Monad @@ -43,40 +46,45 @@ charP x = Parser p p (c:cs) = if c == x then Just (c, cs) else Nothing -satisfy :: (Char -> Bool) -> Parser String -satisfy f = Parser (\s -> Just $ span f s) +satisfy :: (Char -> Bool) -> Parser Char +satisfy f = Parser p + where p [] = Nothing + p (c:cs) = if f c then Just (c, cs) + else Nothing digitsP :: Parser String -digitsP = satisfy isDigit +digitsP = some (satisfy isDigit) -- at least one digit to avoid read exception spacesP :: Parser String -spacesP = satisfy isSpace +spacesP = many (satisfy isSpace) sepBy :: Parser a -> Parser b -> Parser [a] sepBy x sep = (:) <$> x <*> many (sep *> x) -surround :: Parser a -> Parser b -> Parser b -surround surrounding x = surrounding *> x <* surrounding - --- Equation parsers --- 1 * X^0 + 2 * X^1 + 1 * 3 * X^2 = 0 intP :: Parser Int intP = read <$> numStr - where numStr = ((:) <$> charP '-' <*> digitsP) <|> digitsP + where numStr = ((:) <$> charP '-' <*> (spacesP *> digitsP)) + <|> (charP '+' *> spacesP *> digitsP) + <|> digitsP + +naturalP :: Parser Int +naturalP = read <$> digitsP + +-- Equation parsers termP :: Parser Term termP = notConstantP <|> constantP where constantP = (\c -> Term (fromIntegral c) 0) <$> intP notConstantP = (\coef exp -> Term (fromIntegral coef) exp) - <$> intP <*> (between *> intP) + <$> intP <*> (between *> naturalP) where between = spacesP *> charP '*' *> spacesP *> charP 'X' *> spacesP *> charP '^' *> spacesP polynomialP :: Parser Polynomial -polynomialP = sepBy termP (spacesP *> charP '+' *> spacesP) +polynomialP = sepBy termP spacesP equationP :: Parser Equation equationP = (\l r -> Equation l r) |