Proposal: Add Text.Read.maybeRead :: Read a => String -> Maybe a

[Lennart Augustsson]

Because the fail method is an abomination that should never have been
included in the Monad class.

2008/2/7 Jeff Polakow <jeff.polakow at db.com>:

>
> Hello,
>
> Why not allow an arbitrary monad?
>
> readM :: (Monad m, Read a) => String -> String -> m a
> readM errMsg s = case reads s of
>     [(x, "")] -> return x
>     _ -> fail errMsg
>
> -Jeff
>
>
> libraries-bounces at haskell.org wrote on 02/07/2008 01:46:48 PM:
>
>
> > 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
> >
> > Consideration period: 1 week.
> >
> > Patch to Text.Read attached.
> >
> > [attachment "maybeRead.patch" deleted by Jeff Polakow/db/dbcom]
> > _______________________________________________
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> > Libraries at haskell.org
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>
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