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Is there shortcut to initialize fixed size array with constants. For examle, it I need int array[300] with 10 in each of 300 spaces, is there trick to avoid writinig 10 300 times?

econ
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  • Possible duplicate of [Initialization of a normal array with one default value](https://stackoverflow.com/questions/1065774/initialization-of-a-normal-array-with-one-default-value) –  Sep 12 '17 at 17:15
  • With `std::array`, you could implement something to have that array initialized that way, for C-array, simpler would be to fill it. – Jarod42 Sep 12 '17 at 17:20
  • `std::vector v(300,10);` –  Sep 12 '17 at 17:22

2 Answers2

8

Here's a compile time solution that uses initialisation (uses std::array instead of a C array):

template<std::size_t N, typename T, std::size_t... Is>
constexpr std::array<T, N> make_filled_array(
    std::index_sequence<Is...>,
    T const& value
)
{
    return {((void)Is, value)...};
}

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

auto xs = make_filled_array<300, int>(10);
auto ys = make_filled_array<300>(10);
Simple
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6

You can use std::fill_n:

int array[300] = {0};        // initialise the array with all 0's
std::fill_n(array, 300, 10); // fill the array with 10's
Phydeaux
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