On Thu, 5 Aug 2010, David Virebayre wrote:
On Thu, Aug 5, 2010 at 1:11 PM, John Meacham <j...@repetae.net> wrote:
use. This isn't to say ghc is doing the wrong thing, I don't think there
really is a right thing to do here given the broken class specifications
in the report.
I often read that the numerical classes are problematic.
At the same time, there are many programs and packages that rely on
Haskell being that way.
I think the numeric type classes of Haskell 98 are better than the way of
handling numbers in most other existing languages. They are ok for the
applications that do not need polymorphic numeric types.
What would it take to redesign the numeric class so that the new
design eventually becomes the new Haskell standard ? ( not just an
alternative prelude )
Is it doable at all ?
Would a first step be trying to compile all of hackage with the
numeric prelude and see what breaks ?
Almost nothing would compile, because the organization is too different,
not to speak of the more mathematically oriented names of the classes.
If it's doable, how many years would it take to make it happen ?
All functions that use polymorphic numeric types would have to be adapted.
However it would be a great test case for a refactoring tool!
It's even worse: The NumericPrelude is in progress, certainly currently
better than Haskell 98's type classes, but there are known problems.
Sometimes new numeric types are implemented and require to refine or
restructure the classes, again. And there are not only problems with the
numeric type classes, think of Functor, Applicative, Monad, and so on. In
my opinion before trying to move to an improved numerical type hierarchy
we should have class aliases designed, implemented and thoroughly tested
in GHC.
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