Re: [Haskell-cafe] Pearl! I just proved theorem about impossibility of monad transformer for parsing with (1) unbiased choice and (2) ambiguity checking before running embedded monadic action (also, I THREAT I will create another parsing lib)

Are you familiar with selective functors [1]? That library might be helpful in your case.

Thanks for link. This lib is not for me. It allows choosing next computation based on result of previous computation. This is exactly that think, which is forbidden in my task. Because number of possible parses should not depend on results of embedded monadic actions. I already wrote lib based on arrows. It works. I will share code when it is done. == Askar Safin http://safinaskar.com https://sr.ht/~safinaskar https://github.com/safinaskar