Re: [boost] [mpl] broken count and at metafunctions

From: Matt Calabrese (rivorus_at_[hidden])
Date: 2005-08-30 14:32:25

On 8/30/05, Matt Calabrese <rivorus_at_[hidden]> wrote:

> 
> In this case, I guess it's the documentation that must be changed.
> 
> -Matt Calabrese
> 
> 
>  
Actually, I take that back. I believe I was correct in my first post. 
Counting by key is how count should be defined for associative containers, 
just like it is with STL containers. Don't change the documentation for 
count listed in Associative Sequence and map documentation, since counting 
by entire element type in a map wouldn't exactly be very useful and wouldn't 
be consistent with the STL. I stand by my original statement that it's the 
implementation which should be changed, not the documentation. For now, I 
can always just use has_key and use that value as a 1 or a 0 for count, but 
that doesn't exactly help out since I would like my code to also work with 
theoretical associative sequences which can have multiple mapped values per 
key, such as with a theoretical ::boost::mpl::multimap. MPL's count should 
be like STL's count for associative containers.

Also, as a side note, the templates key_type and value_type are great, 
however, can I suggest possibly changing value_type to mapped_type? The 
reason being to be consistent with the STL, since an STL container's 
value_type for a map would be the pair, while the mapped_type is what would 
be the mapped type of the associative sequence. This isn't as big of a deal, 
but if you are concerned with consistency, it might be a good idea to change 
(or at least add a mapped_type template and leave value_type so that it 
doesn't break old code).

-Matt Calabrese