Re: [C++] Derive a class from a tamplate

[corey taylor <corey dot taylor at gmail dot com>]

stefano,

  After taking a quick look at valarray, it seems that operator
overloads that declare operator+ for valarray are non-member
functions.

  You will need to declarea set of operator+ overloads for mvector in
the same style as valarray overloads.  I think this is the problem
you're seeing.

  Is there a reason you're trying to force a copy with the code above?

corey

On 7/31/05, stefano luceri <stefano@communicationfactory.it> wrote:
> Hello to all .... excuse for my bad english
> 
> I've the following problem writing a simple program. I would use the
> metods of std::valarray class adding some self writed method for elemnts
> of double type.
> 
> I've thought something like this:
> 
> /****************************/
> using namespace std;
> 
> class mvector : public valarray<double>
> {
> mvector();
> mvector(int size);
> }
> 
> mvector :: mvector() : valarray<double>() {}
> mvector :: mvector(int size) : valarray<double>(size) {}
> 
> int main()
> {
>    mvector v(3);
> 
>    v = (v+2.0);
> }
> 
> /*****************************/
> 
> Compiling this code I obtain the following error:
> 
> geom.cpp: In function `int main()':
> geom.cpp:38: error: no match for 'operator=' in 'v = std::operator+(const
>   std::valarray<_Tp>&, const _Tp&) [with _Tp = double]((&1.0e+0))'
> geom.cpp:22: error: candidates are: mvector& mvector::operator=(const
> mvector&)
> make: *** [geom.o] Error 1
> 
> Why can't I use the operator = like I do with valarray?
> 
> 
> 
> 
> 
>