yardemo.rb

# Demo of YARD "duck typing" features; see http://yardoc.org
#
# Returns an Array containing two of everything in a collection
# (it need not be an Enumerable; it just has to have an #each method).
#
# @param [#each] collection items to double
# @return [Array] contains two of each item
#
def two_of_everything(collection)
  result = []
  collection.each {|item| result += [item, item]}
  result
end

two_of_everything [1, 'hello', true] # => [1, 1, "hello", "hello", true, true]

The somewhat stilted wording in “collection items to double” appears because YARD strips off the first word and uses it as the parameter name.