(Ruby) How do you check whether a range contains a subset of another range?

The efficient way is to compare the limits

(x.first <= y.last) and (y.first <= x.last)

If you're using Ruby 2.6, you can use Range#cover? with another Range.

(1..5).cover?(2..3)     #=> true
(1..5).cover?(0..6)     #=> false
(1..5).cover?(1...6)    #=> true

You could also convert the ranges to sets, since you're basically doing set intersection here. Might be easier if you are dealing with more than two ranges.

x = (1..10).to_set
y = (5..15).to_set
!(x & y).empty? #returns true (true == overlap, false == no overlap)

Be careful using this with large ranges but this is an elegant way to do it:

(x.to_a & y.to_a).empty?