• John Travers (17/17) Aug 06 2010 Hi,
• bearophile (10/11) Aug 06 2010 Casts are bad, better to avoid them when possible.
• Don (7/28) Aug 07 2010 Welcome! There are quite a few of us who are numerical programmers here,...

John Travers <jtravs gmail.com> writes:

Hi,

I'm investigating if D would be useful to me as a numerical programming
language to replace my current mix of fortran and python.

I'm stuck with a problem which seems odd to me:

    cdouble c1;
    c1 = 2.0;

complains:

    Error: cannot implicitly convert expression (2) of type double to cdouble

The only way I can find to solve this is by doing:

    c1 = cast(cdouble)2.0;

This will drive me crazy, many numeric codes need to multiply complex numbers,
or assign to them, with real numbers. This problem also occurs with imaginary
numbers.

Is there a simple solution to this without covering all my code with casts?

Thanks for any help!

Regards,
John

bearophile <bearophileHUGS lycos.com> writes:

John Travers:
     c1 = cast(cdouble)2.0;

Casts are bad, better to avoid them when possible.
You can do this:

void main() {
  cdouble c1;
  c1 = 2.0 + 0i;
}

But complex numbers will be removed from D, they will become partially library
ones (imaginary ones will probably just removed). I think they will hopefully
keep the same good enough syntax.

Bye,
bearophile

Don <nospam nospam.com> writes:

John Travers wrote:
 Hi,
 
 I'm investigating if D would be useful to me as a numerical programming
 language to replace my current mix of fortran and python.

Welcome! There are quite a few of us who are numerical programmers here, 
and it's one of D's target areas.

 
 I'm stuck with a problem which seems odd to me:
 
     cdouble c1;
     c1 = 2.0;
 
 complains:
 
     Error: cannot implicitly convert expression (2) of type double to cdouble
 
 The only way I can find to solve this is by doing:
 
     c1 = cast(cdouble)2.0;
 
 This will drive me crazy, many numeric codes need to multiply complex numbers,
 or assign to them, with real numbers. This problem also occurs with imaginary
 numbers.

Unfortunately we had to disable implicit casts double->cdouble, because 
it causes problems with function overloading.

So you need to explicitly add the imaginary part.
c1 = 2.0 + 0.0i;