I wondered if that would be possible, a custom for loop. The one I had in mind was the foreach expression from java, which is
for(Container c : Element e){
// do stuff with e
}
I wanted to write it for a custom container I wrote (lets call it cust_cont), which I wanted to work with a foreach loop (like the one from boost). But before reading into iterators and such, I wanted to ask wether I can just implement the loop I want, if need explicitly.
Not sure I understand your question, but yes, you have to implement begin() and end() methods (ideally overloaded on const) in order for iteration to work on your custom container. Also, you need nested iterator and const_iterator types (or typedefs). To summarize, here is what you need:
member types:
MyClass::iterator
MyClass::const_iterator
member functions:
MyClass::iterator MyClass::begin();
MyClass::const_iterator MyClass::begin() const;
MyClass::iterator MyClass::end();
MyClass::const_iterator MyClass::end() const;
Such loop is called range-based loop which is a feature added in C++0x.
So in C++0x, you can write this:
for(Element e : c) {
// do stuff with e
}
where c is a container of object of type Element, and which has defined begin and end as member functions, OR can be passed to begin() and end() functions which are looked up with argument-dependent lookup (ADL), and std is one of the associated namespace(s).
std::begin and std::end, or is it a free function begin and end that can be found via typical ADL ? swap uses ADL, for example.
you can write a macro, something like this:
foreach(Element, e, c) { ... }
See fredoverflow's answer on how to do this for a custom container but since c++11 this became even easier using auto
for(auto element : container)
//do something with element
