[boost] Re: [review] hash functions

From: Daniel James (daniel_at_[hidden])
Date: 2005-03-09 10:53:50

Jaap Suter wrote:
> I would like to second the following:
> 
> "1. The overloads of hash_value for STL containers forces the 
> implementation
> to include <vector>, <list>, etc., which makes the header a little
> heavier than desired."
> 
> I'd say it's not a 'little' heavier but a lot heavier. Can we not put 
> the extensions in their own header files; vector_hash.hpp or something?
> 
> Not everybody has all these containers in a precompiled header already.

While working on this I haven't been using precompiled headers at all. 
And my computer is pretty old. I get the impression that more time is 
spent instantiating templates than parsing header files. But I could be 
completely wrong, I haven't really tested this and it probably varies on 
different compilers.

I think the problem with putting the extensions into a separate header 
is that the hash functions are intended to provide a default 
implementation for hash containers. Users of the library shouldn't have 
to think about including any headers other than the hash container's header.

But it certainly is a valid option - it was the one I used when I first 
started on this.

Daniel