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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, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
Batch operations
(C++17)
Search operations
(C++11)                (C++11)(C++11)

Modifying sequence operations
Copy operations
(C++11)
(C++11)
Swap operations
Transformation operations
Generation operations
Removing operations
Order-changing operations
(until C++17)(C++11)
(C++20)(C++20)
Sampling operations
(C++17)

Sorting and related operations
Partitioning operations
Sorting operations
Binary search operations
(on partitioned ranges)
Set operations (on sorted ranges)
Merge operations (on sorted ranges)
Heap operations
Minimum/maximum operations
(C++11)
(C++17)
Lexicographical comparison operations
Permutation operations
C library
Numeric operations
Operations on uninitialized memory
 
Constrained algorithms
Non-modifying sequence operations
Modifying sequence operations
Partitioning operations
Sorting operations
Binary search operations (on sorted ranges)
Set operations (on sorted ranges)
Heap operations
Minimum/maximum operations
Permutation operations
Numeric operations
Fold operations
Operations on uninitialized storage
Return types
 
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 [firstlast).
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);
    }
};
 
inline constexpr fill_fn fill;

[edit] Example

The following code uses ranges::fill to set all elements of std::vector<int> first to -1, then to 10.

#include <algorithm>
#include <iostream>
#include <vector>
 
void println(std::vector<int> const& vi)
{
    for (int e : vi)
        std::cout << e << ' ';
    std::cout << '\n';
}
 
int main()
{
    std::vector<int> v {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
 
    std::ranges::fill(v.begin(), v.end(), -1);
    println(v);
 
    std::ranges::fill(v, 10);
    println(v);
}

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]