[Feature Request] Introduce Ordering trait

[jayzhan211]

Review Mojo's priorities

• I have read the roadmap and priorities and I believe this request falls within the priorities.

What is your request?

We have EqualityComparable trait for eq and ne.

But, that is not enough to implement comparison function, like sorting

I think we need to introduce trait like

trait OrderingComparable:
  fn __lt__():  1 < 2
  fn __gt__(): 2 > 1
  fn __le__():  1 <= 2
  fn __ge__(): 2 >= 1

There might be a better name for OrderingComparable.

What is your motivation for this change?

Having trait for comparison function

Any other details?

No response

[JoeLoser]

I agree we want this; I haven't thought much about the naming yet. This will enable us to write a generic sorting function and start on algorithms and the like. Did you have a specific use case in mind in applying this in the library or is this just a "known nice to have/something that is needed" from your perspective?

[jayzhan211]

I think it is what we need for List sorting.

#2390

[JoeLoser]

We have a Comparable trait now that serves this purpose. We may rename it to PartialOrd or something, but it's functionally fine for now.