What is the difference between `Range#include?` and `Range#cover?`?
The two methods are designed to do two slightly different things on purpose. Internally they are implemented very differently too. You can take a look at the sources in the documentation and see that .include?
is doing a lot more than .cover?
The .cover?
method is related to the Comparable
module, and checks whether an item would fit between the end points in a sorted list. It will return true even if the item is not in the set implied by the Range
.
The .include?
method is related to the Enumerable
module, and checks whether an item is actually in the complete set implied by the Range
. There is some finessing with numerics - Integer ranges are counted as including all the implied Float
values (I'm not sure why).
These examples might help:
('a'..'z').cover?('yellow')# => true('a'..'z').include?('yellow')# => false('yellaa'..'yellzz').include?('yellow') => true
Additionally, if you try
('aaaaaa'..'zzzzzz').include?('yellow')
you should notice it takes a much longer time than
('aaaaaa'..'zzzzzz').cover?('yellow')
date_range = {:start_date => (DateTime.now + 1.days).to_date, :end_date => (DateTime.now + 10.days).to_date} date_range_to_check_for_coverage = {:start_date => (DateTime.now + 5.days).to_date, :end_date => (DateTime.now + 7.days).to_date} (date_range[:start_date]..date_range[:end_date]).include?((DateTime.now + 5.days).to_date) #true (date_range[:start_date]..date_range[:end_date]).cover?((DateTime.now + 5.days).to_date) #true (date_range[:start_date]..date_range[:end_date]).include?(date_range_to_check_for_coverage[:start_date]..date_range_to_check_for_coverage[:end_date]) #true (date_range[:start_date]..date_range[:end_date]).cover?(date_range_to_check_for_coverage[:start_date]..date_range_to_check_for_coverage[:end_date]) #false
Shouldn't the last line return true ?
The reason I am asking is rubocop flags a conflict when I use include? in place of cover?. And clearly, my logic (to check if the range is included in another range) does not work with cover?.