Re: [boost] [core] Determining interest for two new classes: readonly and newtype

Subject: Re: [boost] [core] Determining interest for two new classes: readonly and newtype
From: Sam Kellett (samkellett_at_[hidden])
Date: 2015-08-18 18:12:04

On 18 August 2015 at 07:57, Vicente J. Botet Escriba <
vicente.botet_at_[hidden]> wrote:

> Le 18/08/15 00:31, Sam Kellett a écrit :
>
>> readonly<T>:
>>>
>>>> [snip]
>>>>
>>>
>>> How both wrappers could work together?
>

i would envision that they should be fine. as readonly is a swapper for
const i would do something like this:

readonly<std::propagate_const<std::string *>> s;

would require testing to make sure that the functionality remains though.

> -----
>>>
>>>> newtype<N, T>
>>>>
>>>> [snip]
>>>>
>>>>
>>> You could take a look at the proposal for Opaque types [1].
>> this is nice. definitely solves the same problem. do you have any idea on
>> the status of that paper? the link is 2013, but i know that doesn't mean
>> much.. is it c++17 expected or later (or ever, atm)?
>>
> See Joel response. I suspect that the last question depends on the work
> the author is able to do.
>
> Any comments about implicit/explicit conversion from/to the opaque type
> and the underlying type?
> Does your class support some of them?
>

it's explicit conversion only, either by casting or dereferencing. the
emphasis is very strict on explicitness as this aims to solve the problem
of accidentally passing, say, a height as a weight or whatever.

> [snip]
>>
>
>>
> that could be quite nice and something i would be happy to look into as
>> part of the move towards boostifying these classes, should people think
>> they have a place here.
>>
>>
> Note that you could also add them conditionally (SFINAE).
>

i'm sorry i'm not sure i follow -- could you elaborate a bit?

> Count with my help if you decide to go on.
>

thanks! i really appreciate it. do you think this should be an extension to
core/utlity? and if so what is the process for that, i know a new library
should be incubated and reviewed, but is that true for extending an
existing library too?