ary[start, length]. out of boundary number giving [ ] output?

Question

While going over the Array class from the Ruby 2.0.0 docs, I noticed something I can't explain. The following is a direct example from the Ruby Docs:

a = [ "a", "b", "c", "d", "e" ]
a[6, 1]                #=> nil
a[5]                   #=> nil
a[5, 1]                #=> []

Could some one explain to me why a[5, 1] has the output [ ]?

Answer 1

The semantics of [] are the same as for slice when two integers are provided. As explained in http://ruby-doc.org/core-2.0/Array.html#method-i-slice, when the first integer points to the end of the array, the empty array will be returned.