Re: [scope] Looking for endorsements and review manager

From: Peter Dimov (pdimov_at_[hidden])
Date: 2023-10-09 16:35:21

Andrey Semashev wrote:
> On 10/9/23 18:33, Peter Dimov via Boost wrote:
> > Andrey Semashev wrote:
> >> Source:
> >>
> >> https://github.com/Lastique/scope
> >>
> >> Docs:
> >>
> >> https://lastique.github.io/scope/libs/scope/doc/html/index.html
> >
> > Question:
> >
> > What is the difference between scope_check<F, C>,
> > scope_success<F, C> and scope_fail<F, C>? Why do we need the
> > second template parameter of the latter two if scope_check is
> > provided?
> >
> > Wouldn't it be clearer if scope_success and scope_fail took a
> > single F parameter?
> 
> The second template parameter is the failure condition checker. It
> exists to allow for checking for different kinds of failure, other than
> whether there is an exception in flight. I wanted to support checking
> for error_codes and similar as an alternative to exceptions.
> 
> For scope_success and scope_fail that template parameter is optional.
> The class templates exist because they were defined in the Fundamentals
> TS (although there the second template parameter is not present and the
> scope guards always unconditionally check for exceptions).
> 
> scope_check is a generalization of scope_success and scope_fail. It does
> not assume exceptions and requires the user to provide his failure
> condition predicate. Other than that, it's functionally equivalent to
> scope_fail. If I was designing the library with no relation to the TS, I
> would probably only provide scope_check.
> 
> I think, there is still a small value in having scope_success and
> scope_fail, since they make the common use case with exceptions a bit
> more concise. But the main reason for their existence is that I want to
> provide the scope guard names that are defined in the TS.

I don't think this answers my question. I agree that scope_success<F>
and scope_fail<F> need to be provided. I'm asking why we need
scope_success<F, C> and scope_fail<F, C>, because it seems to me that
one of these is exactly equivalent to scope_check<F, C> and the other
is the same with the condition reversed.