Re: [boost] [review] Review of Outcome (starts Fri-19-May)

Subject: Re: [boost] [review] Review of Outcome (starts Fri-19-May)
From: Peter Dimov (lists_at_[hidden])
Date: 2017-05-16 23:34:51

Gavin Lambert wrote:
> Future uses "T get()".  This is established standard.
> Smart pointers use "T* get()", which is equivalent to the above.  Also 
> standard.
> Boost Optional uses "T& get()" (although also provides value(), presumably 
> for standard compatibility).
>
> Std Optional uses "T value()".  This is either still experimental or 
> approved for C++17; I'm not entirely sure how far along that is.

It's in C++17.

> The different interfaces of the above seem unfortunate (and Std Optional 
> seems incorrect in this regard to me).
>
> So why not "T get()"?  That's much more consistent with other types.

.get() is when you only have one thing to get; it's for one-element 
containers, where there's no ambiguity as to what is being got.

expected<T, E> and friends have two; the value is .value() and the error is 
.error(), with their matching queries has_value() and has_error().

It's not that get() is unacceptably wrong, but the 
value/has_value/error/has_error convention is legitimate and consistent.