Question

for_each accepts InputIterators :

//from c++ standard template <class InputIterator, class Function>    Function for_each (InputIterator first, InputIterator last, Function f); 

is it ok to change the object in Function f, like this :

struct AddOne {     void operator()(int & x){x = x + 1;} };  std::vector<int> vec(10); std::for_each(vec.begin(),vec.end(),AddOne()); 

This code works in VC++2008 and also with GCC, but is it also portable (legal) code ?
(InputIterators are only guaranteed to be usable as rvalue, in this case they are used as lvalue in AddOne’s operator())

Answer 1

Read this article.

To be pedantic: for_each is a non-modifying sequence operation. The intent is not to modify the sequence. However, it is okay to modify the input sequence when using for_each.