[Haskell-cafe] Are there arithmetic composition of functions?

[Richard O'Keefe]

On 20/03/2012, at 2:21 PM, Chris Smith wrote:

> On Mon, Mar 19, 2012 at 7:16 PM, Richard O'Keefe <ok at cs.otago.ac.nz> wrote:
>> One problem with hooking functions into the Haskell numeric
>> classes is right at the beginning:
>> 
>>    class (Eq a, Show a) => Num a
> 
> This is true in base 4.4, but is no longer true in base 4.5.

I didn't say "GHC", I said "Haskell".

class  (Eq a, Show a) => Num a  where  
    (+), (-), (⋆)    :: a -> a -> a  
    negate           :: a -> a  
    abs, signum      :: a -> a  
    fromInteger      :: Integer -> a  
 
        -- Minimal complete definition:  
        --      All, except negate or (-)  
    x - y            =  x + negate y  
    negate x         =  0 - x

comes straight from the Haskell 2010 report:

http://www.haskell.org/onlinereport/haskell2010/haskellch9.html#x16-1710009

There are other Haskell compilers than GHC.