This test https://github.com/fastruby/fast-ruby/blob/master/code/general/block-apply-method.rb is comparing:

def fast [1, 2, 3].map { |n| do_something(n) } end def slow [1, 2, 3].map(&method(:do_something)) end

We could have one more test:

def other [1, 2, 3].map(&:do_something) end 

Also, I think the names fast and slow shouldn't be used for the methods, the names should describe what the method does, not which one is faster?