std::fill() algorithm

since C++20

// (1)
template< class ForwardIt, class T >
constexpr void fill( ForwardIt first, ForwardIt last, const T& value );

// (2)
template< class ExecutionPolicy, class ForwardIt, class T >
void fill( ExecutionPolicy&& policy,
    ForwardIt first, ForwardIt last, const T& value );

since C++17

// (1)
template< class ForwardIt, class T >
void fill( ForwardIt first, ForwardIt last, const T& value );

// (2)
template< class ExecutionPolicy, class ForwardIt, class T >
void fill( ExecutionPolicy&& policy,
    ForwardIt first, ForwardIt last, const T& value );

until C++17

// (1)
template< class ForwardIt, class T >
void fill( ForwardIt first, 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.
  Overload Resolution

  These overloads participate in overload resolution only if 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 assign.
policy	The execution policy to use. See execution policy for details.

Type requirements

ForwardIt	LegacyForwardIterator
value	Must be writable to first.

Return value

(none)

Complexity

Exactly std::distance(first, last) assignments.

Exceptions

The overloads with a template parameter named ExecutionPolicy report 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

fill (1)

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

Examples

Main.cpp

#include <algorithm>
#include <iostream>
#include <vector>

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