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

[Maciej Marcin Piechotka]

On Tue, 2011-04-19 at 10:02 -0300, Felipe Almeida Lessa wrote:
> 
> Now, that's what I get from reading the code.  I don't remember if it
> is explicitly allowed or forbidden for an iteratee to generate
> leftovers out of nowhere.  My guess is that it doesn't make much sense
> to allow it. 

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']

Regards
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