std::for_each

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Defined in header <algorithm>

template< class InputIterator, class UnaryFunction >
UnaryFunction for_each( InputIterator first, InputIterator last, UnaryFunction f );

Applies the given function object f to the result of dereferencing every iterator in the range [first, last), in order. If InputIterator is a mutable iterator, f may modify the elements of the range through the dereferenced iterator. If f returns a result, the result is ignored.

Contents

[edit] Parameters

first, last - the range to apply the function to
f - the unary function object to be applied (MoveConstructible in (C++11))

[edit] Return value

f. (pre-C++11 version)
std::move(f). (C++11 version)

[edit] Complexity

exactly last - first applications of f

[edit] Equivalent function

[edit] Example

The following example uses a lambda function to increment all of the elements of a vector and then computes a sum of them:

#include <vector>
#include <algorithm>
 
struct Sum {
    Sum() { sum = 0; }
    void operator()(int n) { sum += n; }
 
    int sum;
};
 
int main()
{
 
    std::vector<int> nums{3, 4, 2, 9, 15, 267};
 
    std::cout << "before: ";
    for (auto n : nums) {
        std::cout << n << " ";
    }
    std::cout << '\n';
 
    std::for_each(nums.begin(), nums.end(), [](int &n){ n++; });
    Sum s = std::for_each(nums.begin(), nums.end(), Sum());
 
    std::cout << "after:  ";
    for (auto n : nums) {
        std::cout << n << " ";
    }
    std::cout << '\n';
    std::cout << "sum: " << s.sum << '\n';
}

Output:

before: 3 4 2 9 15 267
after:  4 5 3 10 16 268
sum: 306

[edit] See also

transform
applies a function to a range of elements
(function template)