Re: [boost] Interesting variadic template trick

Subject: Re: [boost] Interesting variadic template trick
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2013-11-18 01:18:14

AMDG

On 11/17/2013 09:55 PM, Andrey Semashev wrote:
> 
>>     template <typename ...T>
>>     struct or_ {
>>         static constexpr bool value = !all_pointers(
>>             ((typename std::conditional<T::value, int, void*>::type)0)...
>>         );
>>     };
>>
>>     template <>
>>     struct or_<> {
>>         static constexpr bool value = false;
>>     };
> 
> 
> It requires N instantiations of std::conditional, doesn't it? In that
> case is it actually faster than the naive recursive instantiation of
> or_?
> 

No it doesn't.  It requires exactly two
instantiations of std::conditional for
all uses of or_.

In Christ,
Steven Watanabe