Re: [boost] [mpl] is there a or_seq like logical metafunction?

From: David Abrahams (dave_at_[hidden])
Date: 2008-04-27 21:50:58

on Fri Mar 07 2008, Steven Watanabe <watanabesj-AT-gmail.com> wrote:

> AMDG
>
> Giovanni Piero Deretta wrote:
>> It seems a perfect application for fold:
>>
>> template<typename Seq>
>> struct or_seq
>>     : mpl::apply<
>>           mpl::fold<mpl::_1, mpl::false_,  mpl::quote2<mpl::or_> >
>>         , Seq
>>       > {};
>>
>> template<typename Seq>
>> struct and_seq
>>     : mpl::apply<
>>           mpl::fold<mpl::_1, mpl::true_,  mpl::quote2<mpl::and_> >
>>         , Seq
>>       > {};
>>   
>
> Not quite, because we want it to short circuit.
> Not to mention that quote2 will not work on and_ and or_.

Yeah, these should be rewritten in terms of mpl::find.
Not sure why mpl::apply was used here either, though maybe I'm missign
something.

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