[Haskell-cafe] Difference between div and /

[Jonas Almström Duregård]

One might expect a == (a/b)*b and other common arithmetic formulas to
hold for division?

/Jonas

On 31 May 2010 14:32, Maciej Piechotka <uzytkownik2 at gmail.com> wrote:
> I started to wonder what is the difference between div and / so they are
> 2 separate symbols.
>
> div:
>  Take a Integral divide and round (down)
>
> (/):
>  Take a Fractional divide and usually round
>
> In some applications I would like to use any of those but it is not
> possible. Is this unification taken into account while reworking numeric
> classes?
>
> I.e. why not:
>
> class Num a => Divisable a where
>    (/) :: a -> a -> a
>
> class (Real a, Enum a, Divisable a) => Integral a where
>    quot :: a -> a -> a
>    rem :: a -> a -> a
>    div = (/)
>    mod :: a -> a -> a
>    x `quotRem` y = (x `quot` y, x `rem y)
>    x `divMod` y = (x `div` y, x `mod` y)
>    toInteger :: a -> Integer
>
> class Divisable a => Fractional a where
>    recip = (1/) :: a -> a
>    fromRational :: Rational -> a
>
> (Example does not take into account other refactoring)
>
> Regards
>
> PS. Why is Fd/cPid etc. Integral or even Num?
> What does (stdin + stderr) `mod` stdout mean (result will be stdin).
>
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