[Boost-users] Re: operators.hpp question.

From: David Abrahams (dave_at_[hidden])
Date: 2004-12-22 14:39:14

Fabio Fracassi wrote:
> Hello,
> 
> I am trying to use the operators.hpp templates to create the following 
> behaviour.
> 
> I have a templated class like this.
> 
> template <class T>
> class example {}
> 
> now I want to do something like this:
> 
> example<SomeType> r;
> example<SomeType> a;
> example<AnotherType> b;
> 
> r = a * b
> 
> To write the multiplication manually I would have to write a function template
> 
> template <class T, class OtherT>
> example<T> operator*(const example<T>& op1, const example<OtherT>& op2);
> 
> So, now my question is: How can this be done with operators.hpp?
> Obviously ... 
> 
> template <class T>
> class example : boost::multiplicative2<example<T>, example<OtherT> >  {
> 
>  template <OtherT> example<T>& operator*=(const example<OtherT>& op);
>  template <OtherT> example<T>& operator/=(const example<OtherT>& op);
> }
> 
> .... won't work, since "OtherT" isn't defined at its first occurrence.
> Is there a way to do what I intended, or do I have to write these operators 
> manually?

You have to write them manually.

Of course you could write your own multiplicative2 that defines
templated friend functions, but it hardly seems worth the trouble.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com