[Haskell-cafe] parsing machine-generated natural text

[Udo Stenzel]

Jason Dagit wrote:
> >   reserved "units." <|> reserved "unit."
> 
> I always struggle with when I need to use 'try' with parsec.
> 
> My understanding is that if 'unit.' appears in the input the first
> parser will parse up to the '.' and then fail and consume the input up
> to that point, leaving the alternative with only the period as input
> so it will also fail.
> 
> So I'm wondering if someone could explain to me what is wrong with my
> understanding of parsec

Nothing at all.  'reserved' actually contains the necessary 'try', a
'notFollowedBy' in order not to swallow parts of longer identifiers and
a useful error message.  I tend to forget 'try', too, or add it in odd
places.  Actually, if ReadP hat better error reporting, I'd recommend
that over Parsec.


Udo.
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