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Subject: Re: [boost] [operators] The future
From: Matt Calabrese (rivorus_at_[hidden])
Date: 2011-10-04 18:38:40

On Tue, Oct 4, 2011 at 6:01 PM, GMan <gmannickg_at_[hidden]> wrote:
> If we're going for C++11, I think the correct way to do this is with a
> single function:
> type operator+(type lhs, const type& rhs)
> {
> lhs += rhs;
> return lhs;
> }
> That should, given that the class implements move-semantics, be sufficient.

If you do that then what does the version look like if the right hand
operand is the moved-from operand? If you do:

type operator+( const type& lhs, type rhs ) { /*...*/ }

Then neither one of the two overloads is a better match over the other,
regardless of which and how many operands are r-values as opposed to
l-values. Being explicit with r-value references and l-value references
disambiguates so that there is no problem.

It is interesting to note that IIRC Boost.Operators already does do the
value-type for operand form, at least on certain compilers, meaning that
current Boost.Operators is already partially move-aware to some extent.

-Matt Calabrese

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