c++ - How to reduce Trait-values of variadic template parameter to one value? -


while experimenting variadic templates came point useful make kind of reduction of trait values 1 final value via operation. use-case me is: 

constexpr bool and(bool lhs, bool rhs){return lhs && rhs;}  struct foo {     template<         typename ...ts>     foo(         ts&&... args)             noexcept(traitreduction<std::is_nothrow_move_constructible, and, ts...>::value)     {/*...*/} }

the problem stl traits single template typed. current working solution is:

template<     template<typename> class traitt,     bool (*operator)(bool,bool),     typename t1,     typename ...ts> struct traitreduction {     static bool const value = traitt<t1>::value; };  template<     template<typename> class traitt,     bool (*operator)(bool,bool),     typename t1,     typename t2,     typename ...ts> struct traitreduction<     traitt,     operator,     t1,     t2,     ts...> {     static bool const value = (*operator)(         traitt<t1>::value,         traitreduction<traitt, operator, t2, ts...>::value); };

my question if stl gives standardized (probably more convenient) solutionfor task? , of course happy here comments on current solution, bad or better.

your solution linear in term of instantiations (and without advantage of short-circuit)

you may in less instantiations (and still without short-circuit)

template <bool...> struct bools{};  template <template <typename> trait, typename ... ts> struct all_of : std::is_same<bools<true, trait<ts>::value...>,                              bools<trait<ts>::value..., true>> {};

you may use std::conjunction linear, short-circuit.

c++1z , folding expression has nice syntax, has less instantiations (but without short-circuit (for instantiation)):

(trait<ts>::value && ...)

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