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std::ranges::fill

From cppreference.com
< cpp‎ | algorithm‎ | ranges
 
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms: std::ranges::copy, std::ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
(C++11)(C++11)(C++11)
(C++17)
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
(C++11)
Binary search operations
Set operations (on sorted ranges)
Heap operations
(C++11)
Minimum/maximum operations
(C++11)
(C++17)

Permutations
Numeric operations
C library
 
Constrained algorithms
Non-modifying sequence operations
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
Binary search operations
Set operations (on sorted ranges)
Heap operations
Minimum/maximum operations
Permutations
 
Defined in header <algorithm>
Call signature
template< class T, std::output_iterator<const T&> O, std::sentinel_for<O> S >
constexpr O fill( O first, S last, const T& value );
(1) (since C++20)
template< class T, ranges::output_range<const T&> R >
constexpr ranges::borrowed_iterator_t<R> fill( R&& r, const T& value );
(2) (since C++20)
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:

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

Contents

[edit] Parameters

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

[edit] Return value

An output iterator that compares equal to last.

[edit] Complexity

Exactly last - first assignments.

[edit] 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);
  }
};

[edit] Example

The following code uses fill() to set all of the elements of a vector of ints to -1:

#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

[edit] See also

assigns a value to a number of elements
(niebloid) [edit]
copies a range of elements to a new location
(niebloid) [edit]
saves the result of a function in a range
(niebloid) [edit]
applies a function to a range of elements
(niebloid) [edit]
copy-assigns the given value to every element in a range
(function template) [edit]