< cpp‎ | algorithm
Defined in header <algorithm>
template< class InputIt, class UnaryFunction >
UnaryFunction for_each( InputIt first, InputIt last, UnaryFunction f );

Applies the given function object f to the result of dereferencing every iterator in the range [first, last), in order.

If InputIt 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

first, last - the range to apply the function to
f - function object, to be applied to the result of dereferencing every iterator in the range [first, last)

The signature of the function should be equivalent to the following:

 void fun(const Type &a);

The signature does not need to have const &.
The type Type must be such that an object of type InputIt can be dereferenced and then implicitly converted to Type.

Type requirements
InputIt must meet the requirements of InputIterator.
UnaryFunction must meet the requirements of MoveConstructible. Does not have to be CopyConstructible

[edit] Return value

f (until C++11)
std::move(f) (since C++11)

[edit] Complexity

Exactly last - first applications of f

[edit] Possible implementation

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

[edit] Example

The following example uses a lambda function to increment all of the elements of a vector and then uses an overloaded operator() in a functor to compute their sum:

#include <vector>
#include <algorithm>
#include <iostream>
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++; });
    // Calls Sum::operator() for each number
    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';


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

[edit] See also

applies a function to a range of elements
(function template) [edit]
range-for loop executes loop over range (since C++11) [edit]
(parallelism TS)
similar to std::for_each except returns void
(function template) [edit]
(parallelism TS)
applies a function object to the first n elements of a sequence
(function template) [edit]