int extension

[thomassth]

Similar to dart-lang/core#624

Since https://github.com/felixblaschke/supercharged is stopping active development, I found the rangeTo and until within are both very useful tool to generate numbered iterates quickly, and brings dart to feature parity with other languages. I think they should be included to this package.

[kevmoo]

CC @lrhn – not sure how I feel about this.

At a minimum, should have tests!

[thomassth]

I've added tests now.

[lrhn]

I'm not totally sold on adding this functionality.

If we do, the naming should be consistent (one is called rangeTo, the other until, so either both or neither should use range), and the implementation might need some tweaking. I'd prefer a an Iterator class which can be inlined by an optimizing compiler where possible, and not allocating a function value for each.

So, I'd say no to this particular implementation, and I'll consider whether we want the functionality or not.
(Discussion should go to dart-lang/core#624).