Re: [boost] Interest in updated expression template library?

Subject: Re: [boost] Interest in updated expression template library?
From: Brook Milligan (brook_at_[hidden])
Date: 2017-01-11 18:34:28

> On Jan 11, 2017, at 2:53 PM, Zach Laine <whatwasthataddress_at_[hidden]> wrote:
> 
> The use of constexpr if is guarded by a macro that is only defined if your
> compiler supports that feature.  The CMake scripts build some test programs
> to determine this.  C++14 compatibility has been extensively tested.
> 
> In general, if you use a compiler that can build Hana, it can almost
> certainly build Yap too (I know of no counterexamples).
> 
> There's also explicit documentation about which compilers are supported:
> 
> https://tzlaine.github.io/yap/doc/html/boost_yap__proposed_/compiler_support.html <https://tzlaine.github.io/yap/doc/html/boost_yap__proposed_/compiler_support.html>

I saw that, which is why I gave it a quick try in the first place.  Given that I found no installation instructions and cmake just built examples and tests, I guess I made the wrong assumption about how to use the library.  I incorrectly just included your files as if they would work directly.  Now a closer look at the code indicates that I have to define the following macro to avoid the constexpr-if statements:  BOOST_NO_CONSTEXPR_IF.  Now it works fine.  Sorry if this should have been obvious, but I am not a user of Hana and have never encountered the need for this macro elsewhere in Boost.

Since I assume this will be necessary for (any?) pre-c++17 compiler, I suggest an addition to the “compiler support” page that mentions this.  Given that there is no dependence of the library on, for example, cmake-generated configuration files (which there shouldn’t be), I feel this is an important bit of information to give to users.

Now at least I can give it a try.  Thanks again for the help.

Cheers,
Brook