std::ranges::fill

template< class T, std::output_iterator<const T&> O, std::sentinel_for<O> S >
constexpr O fill( O first, S last, const T& value );

template< class T, ranges::output_range<const T&> R >
constexpr ranges::borrowed_iterator_t<R> fill( R&& r, const T& value );

The function-like entities described on this page are niebloids, that is:

• Explicit template argument lists may not be specified when calling any of them.
• None of them is visible to argument-dependent lookup.
• When one of them is found by normal unqualified lookup for the name to the left of the function-call operator, it inhibits argument-dependent lookup.

In practice, they may be implemented as function objects, or with special compiler extensions.

Parameters

Return value

An output iterator that compares equal to last.

Complexity

Exactly last - first assignments.

Possible implementation

struct fill_fn {
  template< class T, std::output_iterator<const T&> O, std::sentinel_for<O> S >
  constexpr O operator()( O first, S last, const T& value ) const
  {
      while (first != last) {
          *first++ = value;
      }
 
      return first;
  }
 
  template< class T, ranges::output_range<const T&> R >
  constexpr ranges::borrowed_iterator_t<R> operator()( R&& r, const T& value ) const
  {
    return (*this)(ranges::begin(r), ranges::end(r), value);
  }
};
 
inline constexpr fill_fn fill;

Example

#include <algorithm>
#include <vector>
#include <iostream>
 
int main()
{
    std::vector<int> v{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
 
    namespace ranges = std::ranges;
    ranges::fill(v.begin(), v.end(), -1);
 
    for (auto elem : v) {
        std::cout << elem << " ";
    }
    std::cout << "\n";
 
    ranges::fill(v, 10);
 
    for (auto elem : v) {
        std::cout << elem << " ";
    }
    std::cout << "\n";
}

-1 -1 -1 -1 -1 -1 -1 -1 -1 -1
10 10 10 10 10 10 10 10 10 10

See also