std::ranges::fill_n - cppreference.com (original) (raw)

| Defined in header | | | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | --------------------------- | | Call signature | | | | template< class T, std::output_iterator<const T&> O > constexpr O fill_n( O first, std::iter_difference_t<O> n, const T& value ); | | (since C++20) (until C++26) | | template< class O, class T = std::iter_value_t<O> > requires std::output_iterator<O, const T&> constexpr O fill_n( O first, std::iter_difference_t<O> n, const T& value ); | | (since C++26) |

Assigns the given value to all elements in the range [first, first + n).

The function-like entities described on this page are algorithm function objects (informally known as niebloids), that is:

• Explicit template argument lists cannot be specified when calling any of them.
• None of them are visible to argument-dependent lookup.
• When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Possible implementation
• 5 Notes
• 6 Example
• 7 See also

[edit] Parameters

[edit] Return value

An output iterator that compares equal to first + n.

[edit] Complexity

Exactly n assignments.

[edit] Possible implementation

[edit] Notes

[edit] Example

#include #include #include #include #include   void println(const auto& v) { for (const auto& elem : v) std::cout << ' ' << elem; std::cout << '\n'; }   int main() { constexpr auto n{8};   std::vector<std::string> v(n, "▓▓░░"); println(v);   std::ranges::fill_n(v.begin(), n, "░░▓▓"); println(v);   std::vector<std::complex> nums{{1, 3}, {2, 2}, {4, 8}}; println(nums); #ifdef __cpp_lib_algorithm_default_value_type std::ranges::fill_n(nums.begin(), 2, {4, 2}); #else std::ranges::fill_n(nums.begin(), 2, std::complex{4, 2}); #endif println(nums); }

Output:

▓▓░░ ▓▓░░ ▓▓░░ ▓▓░░ ▓▓░░ ▓▓░░ ▓▓░░ ▓▓░░ ░░▓▓ ░░▓▓ ░░▓▓ ░░▓▓ ░░▓▓ ░░▓▓ ░░▓▓ ░░▓▓ (1,3) (2,2) (4,8) (4,2) (4,2) (4,8)

[edit] See also