Re: [boost] Adding polymorphic_value to boost

On 20 November 2017 at 16:09, Jonathan Coe via Boost wrote:

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On 20 Nov 2017, at 13:37, Peter Dimov via Boost wrote:

Jonathan Coe wrote:

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I'd like to propose adding the class-template `polymorphic_value` to boost.

`polymorphic_value` is designed to allow the compiler to correctly generate special member functions for classes with polymorphic components (It's `any` with an interface).

`polymorphic_value` has been proposed for standardisation in P0201 and has advanced through the Library Evolution group in Albuquerque (Nov 5-10). https://wg21.link/p0201

Has the name "polymorphic_value" been bike-shedded already?

It's a good name in principle, but not good from a usability point of view; too long, too hard to type without errors in the absence of autocompletion.

- poly_value? - any_value? - basic_any?

Also,

- poly

seems to be popular, but it's probably too short.

The name has been bike-shedded. I agree it’s a little long but it conveys meaning pretty clearly to me.

As an opposing data-point I can offer my own experience. I was not previously aware of the PR so the name polymorphic_value came to my attention only yesterday. My initial reaction to the name was to think, "oh, it must be some kind of boost::any with some mechanism for providing operators - something I could use as a polymorphic key in a map" - you know, a kind of value. Clearly I was misled by the suffix _value. It took two readings of the PR to finally understand that this was actually a *pointer* with type-erased cloning. There was no clue to that in the name at all - at least to me. It seems to me that the previous name of cloned_ptr is a better choice. But then I seem to find myself at odds with the thinking of committee contributors more and more these days, so it's probably me. R

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