On Dec 15, 2011, at 5:40 PM, Antoine Latter wrote:
> I said 'combinators', not 'instances'.
Oh! Okay, that was my bad then.
> A lot of popular parsers
> combinators can be written exclusively from (<|>) and empty, but make
> little sense for List and Maybe, and may not even function properly.
> The 'trifecta' package includes a nice reference:
>
> http://hackage.haskell.org/packages/archive/trifecta/0.49.1/doc/html/Text-Trifecta-Parser-Combinators.html
>
> See 'skipSome' through 'chainr1' - I wouldn't be surprised if most of
> these lead to the same infinite loop behavior for Maybe as the stock
> 'many' and 'some' in base.
>
> These sorts of functions are what Alternative is for.
Okay, I see better now what you mean. Thank you.
But then, if so much code based on Alternative makes little sense for List and
Maybe, then maybe this should be a signal they we should remove their instance
from Alternative? After all, we already have the Monad typeclass which gives
them essentially the same functionality.
Cheers,
Greg
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