Difference between index and find_index

Is there a difference between Array#index and Array#find_index? I can’t
see one from reading the docs, but the docs also do NOT say that one
method is just an alias to the other one, so there should be a


The docs aren’t perfect.

When we take alook a the ruby C-source, the comments above the function
rb_ary_index strongly suggest that #index and #find_index are the same.

To confirm this, we ask ruby itself:

a = Array.instance_method :index
b = Array.instance_method :find_index
c = Array.instance_method :rindex
puts a.eql? b # => true
puts a.eql? c # => false

See UnboundMethod#eql?