Re: [Haskell-cafe] Question about the Monad instance for Iteratee (from the enumerator package)

On Fri, Apr 22, 2011 at 5:54 AM, Maciej Marcin Piechotka wrote:

For the record: such code is therefore illegal

abab :: Iteratee Char Identity () abab = continue parseA       where parseA (Chunks ('a':'b':xs)) = parseA (Chunks xs)             parseA (Chunks ('a':[])) = continue parseB             parseA (Chunks xs@(_:_)) = yield () xs             parseA (Chunks []) = continue parseA             parseA EOF = yield () EOF             parseB (Chunks ('b':xs)) = parseA (Chunks xs)             parseB (Chunks xs@(_:_)) = yield () (a:xs)             parseB (Chunks []) = continue parseB             parseB EOF = yield () ['a']

Is it really illegal? I guess you're pointing out a problem with the last line, because it's EOF and we yield something. But that something was given to us in some "continue" step. IMHO, that's perfectly fine. The same thing goes for the other yield in parseB. Cheers, -- Felipe.