std::ranges::fill
From cppreference.com
| Defined in header <algorithm>
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| Call signature |
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| (1) | ||
template< class T, std::output_iterator<const T&> O, std::sentinel_for<O> S > constexpr O fill( O first, S last, const T& value ); |
(since C++20) (until C++26) |
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template< class O, std::sentinel_for<O> S, class T = std::iter_value_t<O> > requires std::output_iterator<O, const T&> constexpr O fill( O first, S last, const T& value ); |
(since C++26) | |
| (2) | ||
template< class T, ranges::output_range<const T&> R > constexpr ranges::borrowed_iterator_t<R> fill( R&& r, const T& value ); |
(since C++20) (until C++26) |
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template< class R, class T = ranges::range_value_t<R> > requires ranges::output_range<R, const T&> constexpr ranges::borrowed_iterator_t<R> fill( R&& r, const T& value ); |
(since C++26) | |
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 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.
Parameters
| first, last | - | the iterator-sentinel pair defining 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 O, std::sentinel_for<O> S, class T = std::iter_value_t<O>>
requires std::output_iterator<O, const T&>
constexpr O operator()(O first, S last, const T& value) const
{
while (first != last)
*first++ = value;
return first;
}
template<class R, class T = ranges::range_value_t<R>>
requires ranges::output_range<R, const T&>
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;
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Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_algorithm_default_value_type |
202403 |
(C++26) | List-initialization for algorithms (1,2) |
Example
Run this code
#include <algorithm>
#include <complex>
#include <iostream>
#include <vector>
void println(const auto& seq)
{
for (const auto& e : seq)
std::cout << e << ' ';
std::cout << '\n';
}
int main()
{
std::vector<int> v{0, 1, 2, 3, 4, 5};
// set all elements to -1 using overload (1)
std::ranges::fill(v.begin(), v.end(), -1);
println(v);
// set all element to 10 using overload (2)
std::ranges::fill(v, 10);
println(v);
std::vector<std::complex<double>> nums{{1, 3}, {2, 2}, {4, 8}};
println(nums);
#ifdef __cpp_lib_algorithm_default_value_type
std::ranges::fill(nums, {4, 2}); // T gets deduced
#else
std::ranges::fill(nums, std::complex<double>{4, 2});
#endif
println(nums);
}
Output:
-1 -1 -1 -1 -1 -1
10 10 10 10 10 10
(1,3) (2,2) (4,8)
(4,2) (4,2) (4,2)
See also
(C++20) |
assigns a value to a number of elements (algorithm function object) |
(C++20)(C++20) |
copies a range of elements to a new location (algorithm function object) |
(C++20) |
saves the result of a function in a range (algorithm function object) |
(C++20) |
applies a function to a range of elements (algorithm function object) |
(C++26) |
fills a range with random numbers from a uniform random bit generator (algorithm function object) |
| copy-assigns the given value to every element in a range (function template) |