[Haskell-cafe] pi

[jerzy.karczmarczuk at info.unicaen.fr]

Yitzchak Gale writes: 

> Dan Piponi wrote:
>> The reusability of Num varies inversely with how many
>> assumptions you make about it.
> 
> A default implementation of pi would only increase usability,
> not decrease it.

Suppose I believe you. (Actually, I am afraid, I have doubts.)
Can you provide some examples of this "increased usability"? 

If possible, with a *relevant* context, which shows that PI should belong
by default to the class Floating (whatever we mean by that...) 

Somehow I do not only think that the default implementation would be good
for nothing, but that putting PI into Floating as a class member, serves
nobody. I would be happy to learn that I am mistaken, but if it is just
to save 5 seconds of a person who wants to pass smoothly between floating
numbers of single and double precision... 

Jerzy Karczmarczuk