Proposal: Add Text.Read.maybeRead :: Read a => String -> Maybe a
ross at soi.city.ac.uk
Thu Feb 7 18:12:43 EST 2008
On Thu, Feb 07, 2008 at 10:46:48AM -0800, Don Stewart wrote:
> This function is typically defined once per project. So its
> about time this safe variant of 'read' made it into the base.
> maybeRead :: Read a => String -> Maybe a
> maybeRead s = case reads s of
> [(x, "")] -> Just x
> _ -> Nothing
I think this is a good idea, though I normally write the equivalent of
maybeRead :: Read a => String -> Maybe a
maybeRead s = case reads s of
[(x, rest)] | all isSpace rest -> Just x
_ -> Nothing
and would prefer not to generalize it to any monad. fail is a wart,
not a design pattern.
> Consideration period: 1 week.
I think that's too short, and the recent fashion of 2 weeks is too short,
even for an uncontroversial change. Some people aren't here continuously,
but I'd still like to get their input.
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