NAME¶

std::fill - std::fill

Synopsis¶

Defined in header <algorithm>
template< class ForwardIt, class T > (until C++20)
void fill( ForwardIt first, ForwardIt last, const T& value );
template< class ForwardIt, class T >
constexpr void fill( ForwardIt first, ForwardIt last, const T& (1) (since C++20)
value );
template< class ExecutionPolicy, class ForwardIt, class T >
void fill( ExecutionPolicy&& policy, ForwardIt first, (2) (since C++17)
ForwardIt last, const T& value );

1) Assigns the given value to the elements in the range [first, last).
2) Same as (1), but executed according to policy. This overload does not participate
in overload resolution unless
std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>
(until C++20)
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>
(since C++20) is true.

Parameters¶

first, last - the range of elements to modify
value - the value to be assigned
policy - the execution policy to use. See execution policy for details.

Type requirements¶

-
ForwardIt must meet the requirements of LegacyForwardIterator.

Return value¶

(none)

Complexity¶

Exactly last - first assignments.

Exceptions¶

The overload with a template parameter named ExecutionPolicy reports errors as
follows:

* If execution of a function invoked as part of the algorithm throws an exception
and ExecutionPolicy is one of the standard policies, std::terminate is called.
For any other ExecutionPolicy, the behavior is implementation-defined.
* If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation¶

template< class ForwardIt, class T >
void fill(ForwardIt first, ForwardIt last, const T& value)
{
for (; first != last; ++first) {
*first = value;
}
}

Example¶

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

// 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};

std::fill(v.begin(), v.end(), -1);

for (auto elem : v) {
std::cout << elem << " ";
}
std::cout << "\n";
}

Output:¶

-1 -1 -1 -1 -1 -1 -1 -1 -1 -1

See also¶

fill_n copy-assigns the given value to N elements in a range
(function template)
copy copies a range of elements to a new location
copy_if (function template)
(C++11)
assigns the results of successive function calls to every element in a
generate range
(function template)
applies a function to a range of elements, storing results in a
transform destination range
(function template)
ranges::fill assigns a range of elements a certain value
(C++20) (niebloid)