How does the range-based for work for plain arrays?

Question

In C++11 you can use a range-based for, which acts as the foreach of other languages. It works even with plain C arrays:

int number         


        

Answer 1

According to the latest C++ Working Draft (n3376) the ranged for statement is equivalent to the following:

{
    auto && __range = range-init;
    for (auto __begin = begin-expr,
              __end = end-expr;
            __begin != __end;
            ++__begin) {
        for-range-declaration = *__begin;
        statement
    }
}

So it knows how to stop the same way a regular for loop using iterators does.

I think you may be looking for something like the following to provide a way to use the above syntax with arrays which consist of only a pointer and size (dynamic arrays):

template 
class Range
{
public:
    Range(T* collection, size_t size) :
        mCollection(collection), mSize(size)
    {
    }

    T* begin() { return &mCollection[0]; }
    T* end () { return &mCollection[mSize]; }

private:
    T* mCollection;
    size_t mSize;
};

This class template can then be used to create a range, over which you can iterate using the new ranged for syntax. I am using this to run through all animation objects in a scene which is imported using a library that only returns a pointer to an array and a size as separate values.

for ( auto pAnimation : Range(pScene->mAnimations, pScene->mNumAnimations) )
{
    // Do something with each pAnimation instance here
}

This syntax is, in my opinion, much clearer than what you would get using std::for_each or a plain for loop.