On Tuesday, 2002-05-28, 18:57, CEST Simon Peyton-Jones wrote:
> Folks
>
> I'm back to tidying up the Haskell Report.
>
> In the Numeric library, there is the useful function
>
> readFloat :: RealFloat a => ReadS a
>
> But you can't use it for reading rationals, because Rational
> isn't in RealFloat!
>
> This is a Royal Pain, and entirely unnecessary. In fact,
> readFloat uses only operations from the RealFrac class,
> so it could equally well have type
>
> readFloat :: RealFrac a => ReadS a
>
> I'm strongly inclined to make this change. It breaks no
> programs, and it fixes a real bug i.e. there is no way to
> read a "103" as a Rational.
>
> Simon
It would be strange to name a function readFloat if its type is
RealFrac a => ReadS a.
I think the function should be named readFrac. For compatibility, one
could put the following into the prelude:
readFloat :: RealFloat a => ReadS a
readFloat = readFrac
And one could mark readFloat as depricated and maybe remove it in some
future version of Haskell.
Ciao, Wolfgang
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