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nine_k • 11/08/2024 • 2 replies • view on HN

But this is not unaided Haskell, it's a parser combinator library, isn't it?

Do you see an obvious reason why a similar approach won't work in Rust? E.g. winnow [1] seems to offer declarative enough style, and there are several more parser combinator libraries in Rust.

[1]: https://docs.rs/winnow/latest/winnow/

Replies

codebje • 11/08/2024

    data Color = Color
        { r :: Word8
        , b :: Word8
        , c :: Word8
        } deriving Show

    hex_primary :: Parser Word8
    hex_primary = toWord8 <$> sat isHexDigit <*> sat isHexDigit
        where toWord8 a b = read ['0', 'x', a, b]

    hex_color :: Parser Color
    hex_color = do
        _ <- char '#'
        Color <$> hex_primary <*> hex_primary <*> hex_primary
Sure, it works in Rust, but it's a pretty far cry from being as simple or legible - there's a lot of extra boilerplate in the Rust.
➕ show 2 replies
mrkeen • 11/08/2024

But it doesn't take much to go from 0 to a parser combinator library. I roll my own each year for advent of code. It starts at like 100 lines of code (which practically writes itself - very hard to stray outside of what the types enforce) and I grow it a bit over the month when I find missing niceties.