pure virtual and template

From:

Philipp Kraus <philipp.kraus@flashpixx.de>

Newsgroups:

comp.lang.c++

Date:

Sun, 27 Jun 2010 20:09:06 +0200

Message-ID:

<i08442$oub$1@online.de>

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Hello,

I try to use abstract classes (only pure virtual function) with
templates for creating my my class structures, but it doesn't work:

my base class:

template<typename T> class distance {
 enum matrixRowType { row = 0, column = 1 };

 public :
 virtual blas::vector<T> calculate( const blas::matrix<T>&, const
blas::matrix<T>&, const matrixRowType& ) const = 0;
 virtual blas::vector<T> calculate( const blas::matrix<T>&, const
blas::matrix<T>&, const blas::matrix<T>&, const matrixRowType& ) const
= 0;
 virtual blas::vector<T> abs( const blas::vector<T>& ) const = 0;
 virtual T calculate( const blas::vector<T>&, const
blas::vector<T>& ) const = 0;
 virtual T calculate( const blas::vector<T>&, const
blas::vector<T>&, const blas::vector<T>& ) const = 0;
 virtual ~distance() = 0;
 };

Now I try to implement these method in my real class with:

template<typename T> class euclid : public distance<T> {}

The compiler shows messages and errors. The blas namespace is used for
boost ublas structurs and I get errors from there like:
error: no type named 'property_map' in .....

If I remove the "public distance<T>" from my euclid class everything
works find. In my opinion I have created a pure virtual class for using
them as a master class. In my subclasses are guaranteed that the
methods all implementated. I need the templates because the types of my
classes are float, double or long double, so I don't want to implement
more classes.

What is my mistake in my design and how I can solve the problems?

Thanks

Phil
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<body>
Hello,
 
I try to use abstract classes (only pure virtual function) with templates for creating my my class structures, but it doesn't work:
 
my base class:
 
template<typename T> class distance {
?? enum matrixRowType { row = 0, column = 1 };
?? ? ? ?
?? public :
?? ? ? virtual blas::vector<T> calculate( const blas::matrix<T>&, const blas::matrix<T>&, const matrixRowType& ) const = 0;
?? ? ? virtual blas::vector<T> calculate( const blas::matrix<T>&, const blas::matrix<T>&, const blas::matrix<T>&, const matrixRowType& ) const = 0;
?? ? ? virtual blas::vector<T> abs( const blas::vector<T>& ) const = 0;
?? ? ? virtual T calculate( const blas::vector<T>&, const blas::vector<T>& ) const = 0;
?? ? ? virtual T calculate( const blas::vector<T>&, const blas::vector<T>&, const blas::vector<T>& ) const = 0;
?? ? ? virtual ~distance() = 0;
? ? };
 
Now I try to implement these method in my real class with:
 
template<typename T> class euclid : public distance<T> {}
 
The compiler shows messages and errors. The blas namespace is used for boost ublas structurs and I get errors from there like:
error: no type named 'property_map' in .....
 
If I remove the "public distance<T>" from my euclid class everything works find. In my opinion I have created a pure virtual class for using them as a master class. In my subclasses are guaranteed that the methods all implementated. I need the templates because the types of my classes are float, double or long double, so I don't want to implement more classes.
 
What is my mistake in my design and how I can solve the problems?
 
Thanks
 
Phil
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