Feature #16990: Sets: operators compatibility with Array

• Status: Open
• Priority: Normal
• Assignee: -
• Target version: -

[marcandre (Marc-Andre Lafortune)]

We currently have set <operator> array work fine:

Set[1] + [2] # => Set[1, 2]

Nothing works in the reverse order:

[1] + Set[2] # => no implicit conversion of Set into Array
# should be:
[1] + Set[2] # => [1, 2]

set-like operators

Note that the situation is particularly frustrating for &, | and -.
If someone wants to do ary - set, one has to do ary - set.to_a which will, internally, do a to_set, so what is happening is set.to_a.to_set!! (assuming ary is over SMALL_ARRAY_LEN == 16 size, otherwise it's still doing in O(ary * set) instead of O(ary)).

The same holds with & and |; see order issue as to why this can not (officially) be done any other way.

Reminder:

ary & ary.reverse # => ary
Set[*ary] & Set[*ary.reverse]  # => Set[*ary.reverse], officially order is indeterminate

[marcandre (Marc-Andre Lafortune)]

• Related to Feature #16989: Sets: need ♥️ added