Re: [pure-lang-users] math.pure

[Albert G. <Dr....@t-...>]

Eddie Rucker wrote:
> What about
> 
> pow (1+2i) 3;

I really shouldn't have opened that can of worms by wrapping the C pow() 
function with Pure's pow. ;-)

I must rethink the purpose of the pow function. It would be silly to 
replicate all functionality we already have with the ^ operator.

In Q pow is just a wrapper for the GMP mpz_pow_ui function, which is 
then extended in rational.q to exact powers of rationals and integers 
with integer exponent. Maybe we should stick to that.

Of course, one can extend that to exact integer powers of complex 
rationals in *polar* notation quite easily, but in rectangular notation 
AFAICS the best you can do is addition-chain exponentiation which only 
works with nonnegative integer exponents and even that needs Theta(log 
n) additions.

That's why I think pow should actually be restricted to the exact 
rational and integer cases, with ^ covering all inexact powers, and 
leave it up to the programmer to extend the former in any manner he 
needs it. At least that was the conclusion we reached when discussing 
this issue in the context of Q.

Comments?

Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag