[boost] Re: Gauging Interest: polar_complex

From: Hubert Holin (Hubert.Holin_at_[hidden])
Date: 2004-11-22 08:51:12

Somewhere in the E.U., le 22/11/2004

   Bonjour

In article 
<6.1.0.6.2.20041120224709.026b7c40_at_[hidden]>,
 Mickey Moore <mgmoore_at_[hidden]> wrote:

> I wanted to gauge whether there might be interest in a class for complex 
> numbers with data stored in polar form.  For some applications, polar 

      I am unsure of any widespread interest in such a thing.

> complex numbers have significant advantages over Cartesian complex (e.g., 
> std::complex) in efficiency and numerical accuracy.  (I spent some time 

      Yes.

> Googling and, somewhat to my surprise, didn't find any freely available 
> versions of this.)
> 
> I have a fairly well developed class that implements this; "boosting" it to 
> be worthy of consideration would probably be straight-forward but 
> non-trivial.  My version of this is of course templated on the contained 
> numeric type.  It is also uses a policy-based design that determines 
> whether or not the polar angle phi is always maintained in principal form 
> or not and what constitutes principal form (default: no, -pi < phi <= pi).
> 
> Thanks, Mickey Moore
> 
> ----------------------------------------
> Mitchell G. (Mickey) Moore, Ph.D.
> mgmoore_at_[hidden]

      The main problems I foresee are in the commingling of the two 
different classes. It is interesting to see a complex number (among 
other ways) either as its two canonical coordinates, or in a polar 
representation, but sometimes we just want to switch between the two for 
a given instance. So I fear a substantial amount of typical run time 
will be spent doing conversions.

      There is another, perhaps deeper, problem to consider, with the 
representation of complex numbers (and others), as evidenced by a thread 
on comp.std.c++ a couple of years back: layout guaranties. People 
wanted, in essence, to be able to break encapsulation when it suited 
them (for efficiency in time-critical code). The discussion also 
encompassed thoughts about the polar representation (which, as you 
remarked, also has advantages). As far as I know, there has been no 
tangible result to that thread.

      In short, I am not sure a library for complex numbers in polar 
form would be worthwile, but I certainly think that if you could make 
the above situation progress (as in: write a formal proposal), it would 
be a great win for us all.

   Bon courage

         Hubert Holin