[phobos] std.complex: updates, bugs, and questions

[Lars Tandle Kyllingstad]

I've committed an update of my std.complex proposal:

   http://github.com/kyllingstad/ltk/blob/master/ltk/complex.d

The current status is as follows:

- Changed mod() to abs(), like Don requested.  I'll implement abs() with 
std.math.hypot() as soon as bug 4023 is fixed.

- Added overloads for the exponentiation operator:
     complex^^complex
     complex^^real
     complex^^integer, w/special cases for 0,1,2,3

- Arithmetic operations now work between different-width complex types, 
as well as between complex and different FP and integer types.

- I tried to make the opOpAssign() functions return by ref, but got hit 
by bug 2460.  This really ought to be fixed now that operator 
overloading is done with function templates, but if it's not a priority 
then I'll use the workaround (i.e. write template(T) { ... }).

- I've used FPTemporary!T where appropriate.


Two questions:

I had a look at the implementation of std.numeric.FPTemporary, and noted 
that it's just an alias for real, regardless of the specified type. 
(Also, the std.math.hypot() function is just defined for the real type.) 
  Can we be sure this is always what the user wants?  Won't using double 
be faster in some cases, or is it so that calculations are done with 
80-bit precision anyway?

As you may have seen, I've put in two different multiplication formulae. 
  I did this because I read that multiplication is slow on some 
architectures, and the first formula has fewer multiplications.  On my 
machine, however, the second (and "standard") one is slightly faster. 
Do you know which architecures this refers to, and are any of them 
relevant for D?

-Lars