Re: [boost] [gsoc16] Static Map Competency test

Subject: Re: [boost] [gsoc16] Static Map Competency test
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2016-02-28 18:51:25

On 28 Feb 2016 at 2:06, Karim Tarabishy wrote:

> > It's not bad. But you can do better, and *much* better if you use a 
> > C++ 1z (17) compiler.
> 
> So the better error part is related to using a better compiler? this is not
> related to how I write my code or it is? It is just I did not pass on an
> elegant compiler error requirement before and I wanted to know if this is
> something related to the way I write the template function or just using a
> better compiler? 

You can do better with just C++ 11/14. A simple solution is a 
static_assert with useful message, but I'd like to hope candidates 
can do better than that.

> "This should fail elegantly and usefully ..."

Think what is actually useful to the end user of the function who has 
supplied it with a string like input. For example, what if the 
supplied input is a wchar_t string? What sort of mechanism would 
allow easy extension and customisation of the types of strings 
hashable, and what kind of compiler error message would fit in with 
that?

> > The "prove" is in bold for a reason: I want to see proof
> 
> So I had generated the assembly before and found that there is no assembly
> code for the function when it is called in a constexpr context, on the other
> hand it is inlined and code exist when it is called in non constexpr
> context. So the proof is just uploading the assembly code? 

The test being performed is to see if you can prove something 
categorically or not in a way amenable to automated unit testing. So 
think "how can I get a computer to prove this" and I'll be pleased.

Niall

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