Re: [boost] [Modularization][optional][functional] boost::none - what do we want it to be?

2014-09-30 9:55 GMT+02:00 Andrey Semashev :

On Mon, Sep 29, 2014 at 8:49 PM, Andrzej Krzemienski wrote:

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Hi Everyone, I know it may be premature to to think about removing every cycle in Boost, but while looking at the cycle reports I found that at least one library is using boost::none, for a purpose different than indicating an uninitialized boost::optional. It is in Boost.Functional:

https://github.com/boostorg/functional/blob/master/include/boost/functional/...

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It uses none_t as a default type for a template type parameter Allocator.

My question is: what do we want boost::none_t to indicate, at least in Boost? 1. A value-semantic alternative to void, that anyone can use? 2. A tag indicating boost::optional<T> without a value?

The answer to this question dictates how we should untie the cycle. I

know

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it is too soon to care about small cycles right now, but my question is more about "the principles".

In my view that use of none_t is not justified. I'm not sure if it can be safely replaced with something different to remove the dependency, but I think it should be done, even if it means breaking some code.

Ok, I created two pull requests. They do not break unit tests at least. https://github.com/boostorg/functional/pull/1 https://github.com/boostorg/functional/pull/2 Regards, &rzej