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

From: vicente.botet (vicente.botet_at_[hidden])
Date: 2008-03-06 14:12:48

Thank you Steven,

----- Original Message ----- 
From: "Steven Watanabe" <watanabesj_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Thursday, March 06, 2008 6:24 AM
Subject: Re: [boost] [mpl] is there a or_seq like logical metafunction?

> AMDG
> 
> vicente.botet wrote:
>> Hello,
>>
>> I needs calculate the mlp::or_ of a sequence of nullary logical 
>> metafunction.
>>
>> This seams quite simple. I have do the following:
>> <code>
>> template <typename Seq>
>> struct or_seq;
>>
>> template <typename Seq, long N>
>> struct or_seq_aux : mpl::or_<
>>    typename mpl::front<Seq>::type,
>>    or_seq<typename mpl::pop_front<Seq>::type>
>>   > {};
>>
>> template <typename Seq>
>> struct or_seq_aux<Seq, 1> : mpl::front<Seq>::type {};
>>
>> template <typename Seq>
>> struct or_seq : or_seq_aux<Seq, mpl::size<Seq>::value> {};
>> </code>
>>
>> Is there a boost or_seq like logical metafunction?
>> Is there a better way to do it?
>>
>> I would be extremely interested in any suggestions.
>>   
> not_<is_same<typename find_if<Seq, _>::type, typename end<Seq>::type> >?
> 
> In Christ,
> Steven Watanabe

I have tested your much more compact solution and it works as expected. 
Here it is with the mpl namespace:

template <typename Seq>
struct or_seq : mpl::not_<
        boost::is_same<typename mpl::find_if<Seq, mpl::_>::type, 
                                    typename mpl::end<Seq>::type> 
     > {};

I don't know if people needs things logical metafunctions like or_seq, 
and_seq could also be the case.

I thing that these two logical metafunctions have a place in mpl. 
What do you thing?

_____________________
Vicente Juan Botet Escriba