[boost] Re: erroneous use of BOOST_STATIC_CONSTANT ?

From: David Abrahams (dave_at_[hidden])
Date: 2004-07-14 17:23:58

Toon Knapen wrote:

> David Abrahams wrote:
> 
> 
>> Ultimately I think the right answer is to use
>>       mpl::integral_c<some_type, some_value>
>>
>> or
>>
>>       mpl::bool_<some_value>
>>
>> etc.
>>
>> everywhere as Paul Mensonides suggested.  One reason is that it
>> centralizes the out-of-line static member definitions.
>>
> 
> I tried this (in the algorithm/string library where I also tested the 
> enum trick for Pavol Droba) and just replaced in 
> algorithm/string/std/string_traits.hpp following lines
> 
>   enum { value = false } ;
>   typedef mpl::bool_< value > type ;
> 
> with
> 
>   typedef mpl::bool_< false > value ;
>   typedef mpl::bool_< value > type ;
> 
> and this evidently results in a compilation error. 

Doesn't surprise me.  You can't just replace an integral constant with a 
type!

> I am not very fluent 
> in mpl but AFAICT this seems like a nice solution but not exactly a 
> drop-in replacement for the current situation.

Not if you do that! I must've failed to make the 2nd half of my posting 
comprehensible.

I don't know how to make it more comprehensible other than to say, 
"please try what I suggested in the 2nd half of my posting".  I guess I 
can also say that bool_< x > has a nested static bool constant ::value 
equal to x.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com