🚀 go-pugleaf

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From: 	Max Motovilov[SMTP:max@int.com]
Sent: 	Friday, January 19, 1996 4:01 PM
To: 	'Eugene Lazutkin'
Subject: 	(for comp.std.c++)  Inherent C++ problem?

Looks like Subj to me, but maybe I misunderstand something or overlooking a 
simple workaround...

Here is the example:

	struct	Complex
	{
		double re, im;

		Complex( double r, double i ) : re( r ), im( i ) {}
		Complex( const Complex& c ) : re( c.re ), im( c.im ) {}
	};

	Complex	operator + ( const Complex& a, const Complex& b )
	{
		return Complex( a.re+b.re, a.im+b.im );
	}

It is all right by now. Consider the following use then:

	Complex a( 1, 0 ), b( 0, 1 );
	Complex c( a+b );

In the last line 3 objects of type Complex are constructed instead of 1, 
namely:

1) Temporary Complex object constructed in 'operator +'
2) Return value of 'operator +' copy-constructed from (1)
3) 'c', copy-constructed from (2)

This is inefficient to the last extreme, moreover it cannot even be 
optimized out since any copy-constructor can theoretically have non-local 
side effects....

To me, the step (2) can be eliminated by certain amendment to the semantics 
of the language while (3) seems to be inherent. I wonder though if 
something could be done about it within the bounds of the current 
standard...

Regards,
...Max...
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