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Subject: Re: [boost] [mpl] multiset
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2015-02-19 09:57:05

On 19 Feb 2015 at 11:59, Bruno Dutra wrote:

> Take hana for example. It is an undeniably impressive piece of work for
> what's been designed, but that, in fact, is constexpr computations, which
> happen to depend on and thus provide type computations mechanisms. Hence it
> suffers of the two shortcomings I mentioned.

The list may not be aware that Boost is funding a GSoC extension for
Hana, which is currently about half way through. It is currently
expected that Hana will reapply for an additional GSoC this summer as
well. Quality software takes time. Remember Louis has a full
coursework load.

Regarding compiler compatibility, Hana almost certainly should work
on GCC 5.0 and Louis nearly has it working on GCC 4.9. I'd imagine
the compiler which will take the longest is as usual MSVC, but there
is a reasonable chance that a VS2017 might just provide enough for
Hana, albeit with many workarounds for the lack of two phase lookup.

The "hackish" syntax you mention is partially unavoidable with C++,
and partially because constexpr was very poorly thought through as a
language feature in that it is much too hard to get constexpr to be
exact. This is regrettable, but the ship has sailed now, just as we
currently overload template syntax with functional compile time
programming which is definitely hackish. If we were sensible, we
would deprecate that in favour of something like D's compile time
programming syntax, but progress on introducing D style syntax has
been oddly partial (functions mostly).


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