Is there a range class in C++11 for use with range based for loops?

Question

I found myself writing this just a bit ago:

template 
class range_class {
 public:
   class iterator {
      friend c         


        

Answer 1

I found that boost::irange was much slower than the canonical integer loop. So I settled on the following much simpler solution using a preprocessor macro:

#define RANGE(a, b) unsigned a=0; a<b; a++

Then you can loop like this:

for(RANGE(i, n)) {
    // code here
}

This range automatically starts from zero. It could be easily extended to start from a given number.

Answer 2

The C++ standard library does not have one, but Boost.Range has boost::counting_range, which certainly qualifies. You could also use boost::irange, which is a bit more focused in scope.

C++20's range library will allow you to do this via view::iota(start, end).