Implement range.count

[nficca]

Implements count for #293.

[windelbouwman]

Instead of using the PyObjectPayload here, use the vm.isinstance type check to determine int type, and objint::get_value to retrieve the BigInt value.

[nficca]

This works for the argument, but won't I still eventually need to use PyObjectPayload to pull out the actual RangeType? Apologies if I misunderstood you, I'm not entirely familiar with this project.

[windelbouwman]

No worries, thank you for your help! The idea is to use PyObjectPayload as little as possible. The objrange.rs file should contain a method get_value which will retrieve the payload for you. This saves a lot of duplicate code for borrow and matching on the payload type. Take a look at the objint::getvalue method for example. It returns you the BigInt contents of the integer. The same should be there for the range type.

Hope this helps!

[windelbouwman]

Btw, the problem with checking strictly on the payload is that this will eventually fail with subclasses. The isinstance check is more thorough and works for subclasses as well!

[nficca]

@windelbouwman I didn't find the objrange::get_value method you mentioned so I've added it myself. I make use of it and objtype::getinstance as you suggested in range_count; I think this is what you meant?

Also, I modified a bunch of the other methods in the file to make use of objrange::get_value as well. Maybe this is beyond the scope of this PR... If so I can move those changes to a separate PR.

[windelbouwman]

This is exactly what I meant. Great job!