Re: Help with Complex numbers

John Fletcher <J.P.Fletcher <at> aston.ac.uk> writes:

> Happy New Year

Dito.

> I am having some success with adapting the Solver example.
> 
> I want to run some cases where the variables are complex 
> numbers.  I have adapted the solver code to be templated and 
> have defined complex as follows
> 
> typedef _Complex double complex;

Have you tried std::complex<double>?
Also I think it is easier define your own data type
containing the complex, just to get sure you do not get 
messed up with the beasty name lookup rules of C++ and mix up
with already define operators. But see above how to change
the definition of class Scalar to achiev the same effect.

> [...]
> When I move it to g++ 4.0.2 it will no longer compile.  It says that a 
> cast from double to double __complex__ is illegal and I have not 
> been able to find any way to initialise a complex variable from an 
> expression.

If you uise your own data type you can add a constructor
which takes an "Expr<T> const &" as argument to get along.

If an own data type is not the option you like, then you could play 
FeaturesOfExpression again to provide a user-defined
conversion operator to whatever

I am not sure if this hits the point.
Could you please provide a short code snippet that already compiles
(or fails to compile?)


> 
> This also throws up the fact that Daixt::Scalar has an internal type 
> of double, and I think I will need a complex version of that.

You are right, Scalar was a quick hack.
This is why it is hidden in namespace Convenience.
Use your own version of Scalar:


template<typename T, typename D> 
class Scalar 
{
public:
  typedef D Disambiguation;
  typedef T NumericalType;

  inline Scalar(const NumericalType& Value = NumericalType()) : Value_(Value) {}
  inline NumericalType Value() const { return Value_; }

private:
  NumericalType Value_;
};

And use std::complex<double> if possible.


best regards,

Markus






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