Re: [boost] Improving the assignment operators of various Boosttypes

Subject: Re: [boost] Improving the assignment operators of various Boosttypes
From: Michael Marcin (mike.marcin_at_[hidden])
Date: 2008-09-10 12:17:39

Peter Dimov wrote:
> Michael Marcin:
> ...
> 
>> It also allows you to support move assignment emulation rather 
>> elegantly using the move library in the sandbox.
> 
> There is no need to use a move library. The point of the above 
> assignment is to take advantage of copy elision, which allows the 
> compiler to construct the rvalue argument directly into 'arg', without a 
> copy. In other words, if you have
> 

For rvalues yes but for lvalues you need move emulation. Which can be 
implemented in the sandbox move library as follows.

class foo
{
public:
    foo();
    foo( T t );
    foo( boost::move_from<foo> other )
    {
       swap( other.source );
    }

    foo& operator=( foo rhs )
    {
       swap( rhs );
    }

    void swap();

    //...
};

T bar();

int main()
{
   foo x;
   foo y( bar() );
   x = boost::move(y);
}

Thanks,

Michael Marcin