I'm having a bit of trouble with the following C++11 code fragment and icpc 15.0.0. This example is compiled correctly by g++ 4.9. I essentially have a templated vector class (with its scalar type T and size N being template arguments).
The variadically templated constructor that checks whether all the arguments are assignable to T& is not found. When I remove the assignable check (which I cannot do because otherwise an ambiguity occurs with the copy-constructor when N=1) the example compiles.
The manually expanded version for 2 arguments compiles. Any idea for a work-around.
// > icpc -v
// icpc version 15.0.0 (gcc version 4.9.0 compatibility)
// > icpc -std=c++11 i_dont_know_what_is_wrong_with_intel.cpp
// i_dont_know_what_is_wrong_with_intel.cpp(39): error: no instance of constructor "Dummy<T, N>::Dummy [with T=double, N=2U]" matches the argument list
// argument types are: (double, double)
// Dummy<double, 2> t{1.0, 2.0};
// ^
// compilation aborted for i_dont_know_what_is_wrong_with_intel.cpp (code 2)
#include <type_traits>
template<typename ...T>
struct All : std::true_type { };
template<typename Head, typename ...Tail>
struct All<Head, Tail ...> : std::conditional<Head::value, All<Tail ...>, std::false_type>::type { };
template<typename T, unsigned N>
struct Dummy
{
// this should work (and does in g++ 4.9), but doesn't
template<typename ...Args, class = typename std::enable_if</*sizeof...(Args) == N && */
All<
std::is_assignable<T&, Args> ...
>::value
>::type>
explicit Dummy(const Args &...args)
{
}
};
// this works
template<typename T>
struct DummyFixed2
{
template<typename Arg1, typename Arg2, class = typename std::enable_if<
All<
std::is_assignable<T&, Arg1>,
std::is_assignable<T&, Arg2>,
>::value
>::type>
explicit DummyFixed2(const Arg1 &arg1, const Arg2 &arg2)
{
}
};
int main(int argc, char const *argv[])
{
DummyFixed2<double> f{1.0, 2.0};
Dummy<double, 2> t{1.0, 2.0};
/* code */
return 0;
}
