attoparsec VS lexy

The basic idea is to create a state monad (usually using the State monad transformer) which contains a string to be parsed, and which also lifts other monad transformers like Except for throwing syntax errors. Or you can use a parser combinator like Parser provided by a parsing library like Megaparsec or Attoparsec that defines an efficient State+Except monad transformer combination for you.

attoparsec

good libraries for parsing: parsec, attoparsec etc.

The more "idiomatic" way would be to use a parser library, e.g. parsec, attoparsec, or megaparsec. But even then I think it would be a lot easier to maintain if you could preserve the angle brackets <> in the input.

- https://hackage.haskell.org/package/attoparsec - https://hackage.haskell.org/package/megaparsec

lexy (https://lexy.foonathan.net/)

https://github.com/foonathan/lexy nakon sto sam se propatio sa errorima od boost spirita, a pegtl mi se nije svidao, ovaj library je dosao kao odusevljenje, a i dokumentacija je iznenadujuce ok

In general, LALR parser generators are more difficult to work with than RD parser combinators. Instead of flex and bison, I'd recommend checking out Boost.Spirit or lexy.

This might be closer: https://github.com/foonathan/lexy

Lexy: https://lexy.foonathan.net/

lexy has something like std::bind with a way to specify fallback values for the placeholders if the arguments aren't provided: lexy::_1.or_default(fallback)