std::for_each

From Cppreference

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.

[edit] Parameters

[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

template<class InputIterator, class UnaryFunction>
UnaryFunction for_each(InputIterator first, InputIterator last, UnaryFunction f)
{
    for (; first != last; ++first) {
        f(*first);
    }
    return f;
}

[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