From:	Jeff Weeks <pweeks AT execulink DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	C++ class interaction and overloading (should be simple answer)
Date:	Sat, 02 Aug 1997 18:13:27 -0400
Organization:	Code X Software
Lines:	58
Message-ID:	<33E3B107.63DEA07F@execulink.com>
NNTP-Posting-Host:	ppp35.neptune.execulink.com
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Hi there...

I've got a C++ problem here.  I've defined a two classes: Vector and
Matrix.  I'd like to be able to do this:

Vector2 = Vector1 * Matrix1

But I can't get that to work.  Is this possible?

What I tried was this (in my Vector class):

class Vector {
  ...
  public:
    inline friend Vector operator * (Matrix& mat, Vector& vect);
  ...
};

inline Vector operator * (Matrix& mat, Vector& vect) {
  Vector v;

  v.x = vect.x * mat.get(0,0) +
        vect.y * mat.get(1,0) +
        vect.z * mat.get(2,0) +
                 mat.get(3,0);

  v.y = vect.x * mat.get(0,1) +
        vect.y * mat.get(1,1) +
        vect.z * mat.get(2,1) +
                 mat.get(3,1);

  v.z = vect.x * mat.get(0,2) +
        vect.y * mat.get(1,2) +
        vect.z * mat.get(2,2) +
                 mat.get(3,2);

  return v;
}
 
I'm afraid I can't remember the error I got (and I'm in Linux now so I
can't check...).  It was something along the lines of, "Can't find
operator to math that expression" :)

I'd really like to get that working, so if anybody has any information
on this, please do tell.  If you need more information, I'll do my best
to supply it.

Thanks a lot,
Jeff


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