NAME

std::ranges::fill - std::ranges::fill

Synopsis

Defined in header <algorithm>
Call signature
template< class T, std::output_iterator<const T&> O,
std::sentinel_for<O> S > (1) (since C++20)
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& (2) (since C++20)
value );

1) Assigns the given value to the elements in the range [first, last).
2) Same as (1), but uses r as the source range, as if using ranges::begin(r) as
first and ranges::end(r) as last.

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

first, last - the range of elements to modify
r - the range of elements to modify
value - the value to be assigned

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

The following code uses ranges::fill() to set all of the elements of a vector of
ints first to -1, then to 10.

// Run this code

#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";
}

Output:

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