From: "knu (Akinori MUSHA)" <knu@...>
Date: 2013-07-30T19:19:21+09:00
Subject: [ruby-core:56268] [ruby-trunk - Feature #6588] Set#intersect?


Issue #6588 has been updated by knu (Akinori MUSHA).


I followed superset?() and the like, and made the new methods accept only a set for the moment, because I couldn't come up with an idea of how to deal with Range.  For example:

- if Set[2].intersect?(1.5..2.5) should return true
- if Set[2].intersect?(3..(1.0/0)) should immediately return false using some knowledge on Range

----------------------------------------
Feature #6588: Set#intersect?
https://bugs.ruby-lang.org/issues/6588#change-40759

Author: marcandre (Marc-Andre Lafortune)
Status: Closed
Priority: Normal
Assignee: knu (Akinori MUSHA)
Category: lib
Target version: next minor


There is `Set#superset?`, `Set#subset?` with their `proper` variants, but there is no `Set#intersect?` nor `Set#disjoint?`

To check if two sets intersect, one can do

  set.intersection(other).empty?

This cycles through all elements, though. To be efficient, one can instead do the iteration manually:

  other.any? { |x| set.include?(x) }

I think it would be natural to add `Set#intersect?` and its reverse `Set#disjoint?`

  class Set
    def intersect?(enum)
      enum.any? { |x| include?(x) }
    end
  end

Maybe it would be worth it to optimize it if enum is a larger Set by starting it with

      return any? { |x| enum.include?(x) } if enum.is_a?(Set) && enum.size > size



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