[boost] Re: [review results] hash functions accepted

From: Daniel James (daniel_at_[hidden])
Date: 2005-03-21 15:30:47

Peter Dimov wrote:
> Thorsten Ottosen wrote:
> 
>> 3. consider if the primary template should not take 1 range parameter
>> and call hash_range;
>>    unordered containers can then be explicitly overloaded when they
>> become available.
>>    this would also have the great effect that subranges like
>> sub_range<string> "just works"
>>    by default
> 
> 
> I don't remember this being discussed during the review, could you 
> please explain it in more detail? Do you mean that hash_value should 
> have a primary template that assumes that its argument is a range? If 
> so, I strongly oppose it. Ranges aren't special from the point of view 
> of hash_value, they shouldn't monopolize the primary template. The 
> proper way to make hash_value work with sub_range<T>, as with any other 
> type, is for sub_range to define a hash_value overload as an inline 
> friend or in its namespace.

I think Thorsten is referring in part to some off list emails, and in 
part to when I wrote (about removing the includes for all the standard 
containers):

> Another possible solution is to just use Boost.Range on anything that 'looks' like a container. But this will break on unordered containers (as equivalent containers can have different sequences).

I forgot to mention that there's no way to tell what 'looks' like a 
container at all. Joaquín replied:

> Too broad IMHO.

So, I think we all rejected the idea. It would be nice if there was a 
way to do something like that, but there isn't.

Daniel