Re: [Haskell-cafe] Re: what is inverse of mzero and return?

Ashley Yakeley writes:

But only some instances (such as []) satisfy this:

(mplus a b) >>= c = mplus (a >>= c) (b >>= c)

Other instances (IO, Maybe) satisfy this:

mplus (return a) b = return a

I think mplus should be separated into two functions.

This would prevent using mplus in a single parser which - depending on the underlying monad used - backtracks or not. -- __("< Marcin Kowalczyk \__/ qrczak@knm.org.pl ^^ http://qrnik.knm.org.pl/~qrczak/