Essential Books

Turn a sequence of indices into copies of an element

suggest change

Expanding the parameter pack of indices in a comma expression with a value creates a copy of the value for each of the indices. Sadly, gcc and clang think the index has no effect and warn about it (gcc can be silenced by casting the index to void): 

#include <algorithm>
#include <array>
#include <iostream>
#include <iterator>
#include <string>
#include <utility>

template <typename T, std::size_t... I>
std::array<T, sizeof...(I)> make_array(T const& value, std::index_sequence<I...>) {
    return std::array<T, sizeof...(I)>{ (I, value)... };
}

template <int N, typename T>
std::array<T, N> make_array(T const& value) {
    return make_array(value, std::make_index_sequence<N>());
}

int main() {
    auto array = make_array<20>(std::string("value"));
    std::copy(array.begin(), array.end(),
              std::ostream_iterator<std::string>(std::cout, " "));
    std::cout << "\n";
}
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std::integer_sequence:
* Turn a std::tuple... into function parameters
* Create a parameter pack consisting of integers
* Turn a sequence of indices into copies of an element
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143 Digit separators
144 C++ Containers
145 Arithmetic meta-programming
146 Contributors