Re: [boost] Adding polymorphic_value to boost

On 21 Nov 2017, at 17:30, Seth via Boost wrote:

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On 21-11-17 09:45, Jonathan Coe via Boost wrote: Do you have sample code you might be able to share to illustrate this point: "Sometimes (in a comms-based system, often) even though the handle object's interface is const, and accessor will do some internal work which may need to mutate the implementation (even on another thread)." I'm afraid this example is sufficiently removed from my day-to-day experience that I struggle to see what you mean without code.

I'm not sure, but I'm seeing `handle` as something completely different, unrelated to `polymorphic_value`.

The implementation of a handle's body could benefit a lot from `polymorphic_value`, but

- in my mind a `polymorphic_value` has - by definition - value semantics, and a such _requires_ const-propagation always (because that's consistent witht he core language value semantics).

- likewise, the const-ness of a handle never propagates to it's body

Different patterns, different semantics, different type, I think

Cheers,

Seth

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I would agree that polymorphic_value and cloned_ptr solve different problems. My proposed addition to boost is polymorphic_value, I could possibly be convinced to propose cloned_ptr too. Regards Jon