| 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.
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:
The signature does not need to have |
| Type requirements | ||
- InputIt must meet the requirements of InputIterator. | ||
- UnaryFunction must meet the requirements of MoveConstructible. Does not have to be CopyConstructible | ||
Return value
f | (until C++11) |
std::move(f) | (since C++11) |
Complexity
Exactly last - first applications of f.
Possible implementation
template<class InputIt, class UnaryFunction>
UnaryFunction for_each(InputIt first, InputIt last, UnaryFunction f)
{
for (; first != last; ++first) {
f(*first);
}
return f;
} |
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';
}Output:
before: 3 4 2 9 15 267 after: 4 5 3 10 16 268 sum: 306
See also
| applies a function to a range of elements (function template) | |
| range-for loop | executes loop over range (since C++11) |
| (parallelism TS) | similar to std::for_each except returns void (function template) |
| (parallelism TS) | applies a function object to the first n elements of a sequence (function template) |
Please login to continue.