ANNOUNCE: yap-0.0 - yet another prelude

Henning Thielemann lemming at
Wed Aug 10 16:46:43 CEST 2011

On Wed, 10 Aug 2011, Paterson, Ross wrote:

> Yet another restructuring of the Prelude numeric classes on algebraic lines, proposed for a revision of the Haskell Prelude:

A nice lightweight design, both in terms of the use of type extensions and 
import dependencies, that should people encourage to use it, when they are 
afraid of changing to a more radical approach like numeric-prelude. I 
would have prefered the name AdditiveGroup to AbelianGroup, since with '+' 
and '-' and '0' I associate more than just the laws of an Abelian group. 
The multiplicative group of rational numbers is abelian, too.

  I also like the Quantity datatype. It can be used with any framework for 
type-encoded physical units. I have for instance a Haskell98 approach, 
that could be sepearated from numeric-prelude:
  In this approach I encode composed units using type constructors like Mul 
and Div and the user is responsible for showing that (Mul a b) is 
equivalent to (Mul b a). Sure, its cumbersome, but Haskell 98 and I hope 
you do not need those proofs very often.

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