for_each

std::for_each applies a unary callable to each element of its range. The range is given by the input iterators.

UnFunc std::for_each(InpIt first, InpIt second, UnFunc func)
void std::for_each(ExePol pol, FwdIt first, FwdIt second, UnFunc func)

std::for_each when used without an explicit execution policy is a special algorithm because it returns its callable argument. If you invoke std::for_each with a function object, you can store the result of the function call directly in the function object.

InpIt std::for_each_n(InpIt first, Size n, UnFunc func)
FwdIt std::for_each_n(ExePol pol, FwdIt first, Size n, UnFunc func)

std::for_each_n is new with C++17 and applies a unary callable to the first n elements of its range. The range is given by an input iterator and a size.

std::for_each

// forEach.cpp
...
#include <algorithm>
...
template <typename T>
class ContInfo{
public:
  void operator()(T t){
    num++;
    sum+= t;
  }
  int getSum() const{...