[Haskell] Re: sizeFM type

Simon Peyton-Jones simonpj at microsoft.com
Tue Apr 27 09:28:32 EDT 2004


Could we move this debate to Haskell-café?

Simon

| -----Original Message-----
| From: haskell-bounces at haskell.org [mailto:haskell-bounces at haskell.org] On Behalf Of Serge D.
| Mechveliani
| Sent: 27 April 2004 05:49
| To: Ketil Malde
| Cc: haskell at haskell.org
| Subject: Re: [Haskell] Re: sizeFM type
| 
| On Mon, Apr 26, 2004 at 10:09:18PM +0200, Ketil Malde wrote:
| > "Serge D. Mechveliani" <mechvel at botik.ru> writes:
| >
| > > Alexander is right.
| > >
| > > Also as  Integer  has more sense than  Int,
| > > I would suggest for the future standard Haskell library to have
| > > Integer as default. For example:
| > >                                 length      :: [a] -> Integer
| > >                                 smallLength :: [a] -> Int
| >
| > Hmm...isn't it possible to use a class here?  Perhaps even Num?
| >
| >     class Num a where ....
| >         :
| >         length :: [b] -> a
| >         :
| >
| 
| I think, for many functions, like  length,  it is most natural to
| return  Integer  only.
| And it is also natural for many instances (domains) D to provide
| maps like  toInteger, fromInteger.
| Just follow mathematics.
| 
| Example:           length xs                :: (Rational, Rational)
| looks unnatural,
| but                fromInteger (length xs)  :: (Rational, Rational)
| looks natural.
| 
| -----------------
| Serge Mechveliani
| mechvel at botik.ru
| 
| 
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