Range evaluation in Ruby

In Ruby, whenever we evaluate if an object lies inside a range, we can use cover? to ask Ruby to figure it out logically using the lower and upper limit; rather than using include? which would instantiate each element of the range and then perform the evaluation on each instance of the range.

Using: include?

(1..10).include?(7)      # true

Compares to performing all these evaluations:

1 == 7     # false
2 == 7     # false
3 == 7     # false
4 == 7     # false
5 == 7     # false
6 == 7     # false
7 == 7     # true

Using: cover?

(1..10).cover?(7)      # true

Compares to performing this single evaluation:

7 >= 1 && 7 <= 10      # true

cover? has performance advantages on large ranges or on more complex objects; like Date objects.

You can find more information about cover? and include? on the ruby-doc website.