[Boost-users] Need help understanding boost::operators::dividable

From: Scott, Steven (Steven.Scott_at_[hidden])
Date: 2007-06-21 11:39:10

I'm sure the answer to this is out there somewhere, but I'm
having trouble finding it.  (wearing flame-retardant clothes...)

I want to use boost::operators::field_operators to generate all
the mathematical operators to allow Vector/scalar arithmetic.
Everything works fine except for dividing scalars by vectors.

Class Vector looks like this:

    class Vector 
      : public std::vector<double>, 
      boost::field_operators<Vector,
                             boost::field_operators<Vector, double> >
    {
      // required operator+=, -=, *=, /= defined here.
     };  

Now if I write:

   double x(3.0);
   Vector v(5), w;
   v[0] = 1; v[1] = 2; v[2] = 3; v[3] = 4; v[4]=5;

    w = 3+v;  // works fine
    w = v+3;  // works fine
     ... // subtract and multiply work on both sides
    w = v/x;  // works fine
    w = x/v;  // fails...         

I think the failure happens because of the way operator/ 
defined for mixed types something like this:

T operator/(U u,T t)
{
   T ans(u);
   ans/=t;
   return ans;
}

which is not what I need.  Is there a way I can change the way
operator/(double,Vector) works in this one case, but keep the really
convenient 
definitions generated by field_operators otherwise?

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