ANNOUNCE: yap-0.0 - yet another prelude

Henning Thielemann lemming at
Fri Aug 12 01:33:46 CEST 2011

On Fri, 12 Aug 2011, Paterson, Ross wrote:

> wren ng thornton [wren at] writes:
>> On 8/10/11 9:53 AM, Paterson, Ross wrote:
>>> Yet another restructuring of the Prelude numeric classes on algebraic lines, proposed for a revision of the Haskell Prelude:
>> Very nice in its simplicity, but it suffers from the same problem as all
>> the other attempts I've seen. Namely it ignores the importance of
>> semirings and runs headlong towards fields and beyond. The {(-), abs,
>> signum, negate} methods really must be broken out from (+).
> abs and signum are already split off, but it could be further split, with
> Monoid and Semiring subclasses of AbelianGroup and Ring, and that
> would fit nicely with a Natural type.  I wasn't sure it was worth it
> (having + operate on lists might be confusing for beginners).

Having a (+) is possible for both Additive Group or more fine-grained 
classes, isn't it? There is still the question, whether (+) lists shortens 
like zipWith (+) or expands to the longer list. Or do you even mean to 
define (+) as being (++) on lists? (Which would be also non-commutative, 
that is, non-Abelian.)

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