3 ms·

(And is a really great example motivating both monads and monad transformers, for the curious!)

• freyrs3 13y ago
  The shallow DSL in the LLVM monad is really nice, it looks almost like the IR itself but you can abstract over it and compose it with other code. DSLs are often overlooked when talking about monad use cases.
  • tel 13y ago
    I really need to explore LLVM in more detail at some point.
• tel 13y ago
  For the extra curious, here's a little Parser (untested, poor design, but generally the right idea) newtype Parser a = Parser { unParser :: MaybeT (State String) a } deriving ( Functor, Applicative, Alternative, Monad, MonadPlus, MonadTrans, MonadState String ) -- why write boilerplate when the -- compiler will for you? runParser :: Parser a -> String -> Maybe a runParser input = flip evalStateT input . runMaybeT -- | Parses a single character if it passes a predicate satisfy :: (Char -> Bool) -> Parser Char satisfy p = do (c:cs) <- get guard (p c) put cs return c char :: Char -> Parser Char char c = satisfy (== c) -- | Parses a whole string string :: String -> Parser String string = mapM char -- | Converts a parser to be surrounded by parentheses parens :: Parser a -> Parser a parens p = char '(' *> p <* char ')'