> On Jan. 3, 2016, 11:55 p.m., Benjamin Hindman wrote:
> > 3rdparty/libprocess/include/process/future.hpp, lines 228-230
> > <https://reviews.apache.org/r/41460/diff/1/?file=1166979#file1166979line228>
> >
> > Why do we need to capture/alias the type `F` as `G` again and then use
> > it in `std::result_of<G()>::type`? Why can't we just use `F` there again?
>
> Michael Park wrote:
> We could if there was a guarantee that the default template arguments are
> instantiated left-to-right. I'm not sure whether such guarantee exists and
> would prefer not rely on it even if it did.
>
> This way, it's required that the default argument to `G` be instantiated
> first, and there's no chance of `std::result_of` being instantiated with `F`
> if `F` is the result of a `std::bind`.
Synced with BenH offline about this. The SFINAE evaluation is not guaranteed to
be performed in lexical order until C++14. Once we get to C++14 we can write
something like:
```cpp
template <
typename F,
typename = typename std::enable_if<!std::is_bind_expression<
typename std::decay<F>::type>::value>::type,
typename = typename std::result_of<F()>::type>
...
```
Meanwhile, we simply inline the `G`.
- Michael
-----------------------------------------------------------
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-----------------------------------------------------------
On Jan. 6, 2016, 2:27 a.m., Michael Park wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/41460/
> -----------------------------------------------------------
>
> (Updated Jan. 6, 2016, 2:27 a.m.)
>
>
> Review request for mesos, Benjamin Hindman, Alex Clemmer, and Joris Van
> Remoortere.
>
>
> Bugs: MESOS-4228
> https://issues.apache.org/jira/browse/MESOS-4228
>
>
> Repository: mesos
>
>
> Description
> -------
>
> The Standard (C++11 through 17) does not require `std::bind`'s function call
> operator to SFINAE, and VS 2015's doesn't. `std::is_bind_expression` can be
> used to manually reroute bind expressions to the 1-arg overload, where
> (conveniently) the argument will be ignored if necessary.
>
> Follow-up from [r40114](https://reviews.apache.org/r/40114/).
>
>
> Diffs
> -----
>
> 3rdparty/libprocess/include/process/future.hpp
> bcb5668565298825056f1b48d48efe12d2e56e7c
>
> Diff: https://reviews.apache.org/r/41460/diff/
>
>
> Testing
> -------
>
> `make check` on OS X, compiled on Windows.
>
>
> Thanks,
>
> Michael Park
>
>
