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Subject: Re: [boost] expected/result/etc
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2016-02-04 17:34:52

On 5/02/2016 04:22, Niall Douglas wrote:
> On 4 Feb 2016 at 14:45, Sam Kellett wrote:
>> redefining a macro in somebody else's 'namespace' is akin to opening up the
>> std namespace to redefine vector.
> This is exactly what my Boost-lite emulation already does.
> The problem is when you include my stuff first and then include Boost
> without telling my stuff you actually want to use Boost, then Boost's
> definitions collide with my emulated ones.
> If Boost did as you suggested there would be no warnings, and I'm
> defining the same functionally speaking thing as Boost is so there
> should be no breakage (insert many caveats omitted for brevity here).

I think what Sam was trying to get at is that instead of declaring
things in the boost namespace, your abstraction layer should declare
things in some unique namespace (mostly as typedefs and usings from
either std:: or boost:: as appropriate), and then your code that depends
on this should exclusively use your abstraction layer namespace, not the
boost namespace.

This will avoid generating any conflicts or warnings even if Boost and
your emulation are included at the same time. Though the potential
downside is that in cases where you want it to use the Boost version, it
might not due to the include order, and you could end up with some
components using Boost and others not (although that should generate
link errors).

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