Array#first returns different classes based on arg

Ruby's Array#first will have very different return types based on what arguments you provide. Without an argument, it will return nil or object. With an argument, it will always return a new array; even if your argument is 1 or 0.

a = [:foo, 'bar', 2]
a.first 
# => :foo

a.first(1) 
# => [:foo]

a.first(0)
# => []

With an empty array:

[].first
# => nil

[].first(1)
# => []

[].first(0)
# => []