C++ Operators			    Bob Walton, 7/16/96

The name `operator ==' can be used like a function name:

	x == y   <=====>  operator == ( x, y )

This is just a matter of surface syntax.  But it allows
us to define operators.  For example:

  enum color { RED, GREEN, ANY };

  bool operator == ( color x, color y )
  {
      if ( int ( x ) == int ( ANY ) ) return true;
      else if ( int ( y ) == int ( ANY ) ) return true;
      else return int ( x ) == int (  y );
  }

The operator == above implements the rewrite equations:

  x == ANY	===> true
  ANY == y	===> true
  x == y	===> int( x ) == int( y )
			if the previous cases
			do not apply

Then:

  RED == GREEN	===> false
  RED == RED	===> true
  RED == ANY	===> true
  ANY == GREEN	===> true
  operator == ( RED, ANY ) ===> RED == ANY
			   ===> true


C++ does NOT allow you to redefine an existing operator
definition.  E.g.

  foo * operator + ( foo * p, int i ) { ... }

is ILLEGAL as p+i is predefined.

In fact, C++ requires any operator you define to have at
least one argument that is a class (or struct or union)
or enum.

Existing versions of some C++ compilers (g++) require
operators to have a class or struct argument in order to
work correctly.