[Haskell-cafe]  == 
derek.a.elkins at gmail.com
Sat May 30 20:05:27 EDT 2009
On Fri, May 29, 2009 at 5:36 AM, Max Rabkin <max.rabkin at gmail.com> wrote:
> On Fri, May 29, 2009 at 12:29 PM, Paul Keir <pkeir at dcs.gla.ac.uk> wrote:
>> f''' = (::[()]) == (::[()])
>> (Very pretty.)
>> So why doesn't ghc have 'default' instances?
> It does. I believe Num defaults to Integer and then to Double.
> Generally, though, defaults are convenient in exploratory usage but
> confusing in compiled code. In compiled code, you don't want arbitrary
> choices of defaults to affect performance and correctness.
> I've had programs run much slower than expected because the types
> defaulted to Integer rather than Int.
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