How to determine if one array contains all elements of another array

Question

Given:

a1 = [5, 1, 6, 14, 2, 8]

I would like to determine if it contains all elements of:

a2 = [2, 6, 15]

In this case the result is false.

Are there any built-in Ruby/Rails methods to identify such array inclusion?

One way to implement this is:

a2.index{ |x| !a1.include?(x) }.nil?

Is there a better, more readable, way?

Answer 1

a = [5, 1, 6, 14, 2, 8]
b = [2, 6, 15]

a - b
# => [5, 1, 14, 8]

b - a
# => [15]

(b - a).empty?
# => false