Stream: announcements

Topic: Breaking change: List.sort API

Luke Boswell (Aug 27 2026 at 07:45):

As of this PR https://github.com/roc-lang/roc/pull/9832

• Replaces the old LT/EQ/GT ordering tags with FirstBeforeSecond, Equivalent, and SecondBeforeFirst
• Adds default_cmp to built-in types that have a natural default ordering, including numbers and tuples. Strings intentionally do not gain an implicit default ordering.
• Adds the public list APIs:
  - List.sort
  - List.sort_by
  - List.sort_with
  - List.sort_reversed
  - List.sort_by_reversed
  - List.sort_with_reversed
• Implements stable List.sort_with as a compiler low-level operation backed by Fluxsort/Quadsort

Thank you to @Jonathan and @Brendan Hansknecht for their work on this.

Luke Boswell (Aug 27 2026 at 07:50):

Also if anyone is interested here are the fuzz targets I used to help validate the implementation and also find/fix some bugs :bug:

https://github.com/lukewilliamboswell/roc-fuzz/pull/8

Romain Lepert (Aug 27 2026 at 10:05):

:smiling_face_with_tear: on the FirstBeforeSecond, Equivalent, and SecondBeforeFirst

#ideas > Sorting tuples? @ 💬

Karakatiza (Aug 27 2026 at 11:23):

I realize such a feedback is too late and I haven't followed this at all, but was something like "LeftComesFirst" and "LeftComesLast" or "RightComesFirst" considered?

Jonathan (Aug 27 2026 at 11:29):

It was ruled out because it is not uncommon for left and right to be mixed up.

Luke Boswell (Aug 28 2026 at 04:01):

Sorry for the spam... here is another update on this https://github.com/roc-lang/roc/pull/10975

• replace the default_cmp with order_relative_to
• replace [FirstBeforeSecond, Equivalent, SecondBeforeFirst] with [Before, Same, After]

match a.order_relative_to(b) {
    Before => ...
    Same => ...
    After => ...
}

Last updated: Sep 03 2026 at 15:16 UTC