Re: [boost] Array in Unordered Map

Subject: Re: [boost] Array in Unordered Map
From: Olaf van der Spek (ml_at_[hidden])
Date: 2012-04-30 17:02:37

On Mon, Apr 30, 2012 at 10:11 PM, Daniel James <dnljms_at_[hidden]> wrote:
> On 30 April 2012 18:12, Olaf van der Spek <ml_at_[hidden]> wrote:
>> Hi,
>>
>> What's the right way to get an array into an unordered map?
>>
>> This one works on VC10, but GCC appears to look for the hash_value
>> function in namespace std.
>> What's the right way to do this?
>
> As far as I know gcc is correct. Functions are only visible if they're
> available at the point of the call to hash_value in the source code,

Are both VC10 and VC11 broken then?

> or via ADL at the point of instantiation. So you need to do one of: a)
> write hash_value before including the hash header,

A bit hard, as I need hash_range().

> b) write hash_value
> in the std namespace,

Doesn't work with VC10.

c) specialize boost::hash, d) use trunk, which
> supports std::array or

Not an option, the software should be compilable on Debian, CentOS, RHEL, etc.

> e) patch your copy of boost.

See D

> 'a' is pretty
> fragile, 'b' isn't standards compliant, 'd' and 'e' might not be
> possible so 'c' is possibly the best thing to do - it also won't clash
> with boost::hash_value when boost 1.50 is released. Specializing
> boost::hash isn't really recommended in general, but if there's no
> other solution...

I'll give C a try, thanks.

-- 
Olaf