Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!zaphod.mps.ohio-state.edu!usc!jarthur!spectre.ccsf.caltech.edu!spectre.ccsf.caltech.edu!myers
From: myers@over.cs.caltech.edu (Bob Myers)
Newsgroups: comp.lang.c++
Subject: Operator overloading: good style?
Message-ID: <MYERS.90Feb18231352@over.cs.caltech.edu>
Date: 19 Feb 90 07:13:52 GMT
Sender: news@spectre.ccsf.caltech.edu
Organization: California Institute of Technology
Lines: 50
In-Reply-To: pcg@aber-cs.UUCP's message of 18 Feb 90 19:12:33 GMT


I'd like to hear opinions on operator overloading from a stylistic viewpoint.
When is it a good idea?

There are some cases that seem very clear to me, but others I have used
seem a little questionable to me now.

Example:

I had a vector3d class I implemented when I first learned C++ about 3 years
ago:

----------

class vector3d {
	double x, y, z;
public:
    vector3d()                                        { x=0;  y=0;  z=0;  }  
    vector3d(double x0, double y0, double z0)         { x=x0; y=y0; z=z0; }

       vector3d operator-();                        // Vector negation
       vector3d operator+(const vector3d&);         // Vector addition
       vector3d operator-(const vector3d&);         // Vector subtraction
       vector3d operator*(double);                  // Scalar multiplication
friend vector3d operator*(double, const vector3d&); // Scalar multiplication
       vector3d operator/(double);                  // Scalar division
       vector3d operator%(const vector3d&);         // Cross product

       vector3d operator^(double);                  // x-axis rotation
       vector3d operator&(double);                  // y-axis rotation
       vector3d operator|(double);                  // z-axis rotation

     //	... etc ...
}

----------

You get the idea.  Anyway, some of this stuff seemed like obvious
candidates for overloading: + - * / for example.  However, the
overloaded % ^ & | are not at all related to the "standard" C
operators. They seemed to be useful operators at the time, however,
most particularly the % for cross product.

But what about the rotation operators? I found them useful, but will
anyone be able to read my code later? It is, I'll admit, difficult to
remember which operator rotates the vector about which axis.  Is this
sort of thing a bad candidate for overloading? What do you think?

---------------------------------------------------------------------------
Bob Myers                                      myers@through.cs.caltech.edu