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module Enumerable
# Returns all items that are equal in terms of the supplied block.
# If no block is given objects are considered to be equal if they return the
# same value for Object#hash and if obj1 == obj2.
# No guarantee about the order of the elements in the resulting array is made.
#
# Note: The result will be an array if you supply no block and a hash otherwise.
#
# [1, 2, 2, 3, 4, 4].commonality # => { 2 => [2], 4 => [4] }
#
# ["foo", "bar", "a"].commonality { |str| str.length }
# # => { 2 => ["foo, "bar"] }
#
# # Returns all persons that share their last name with another person.
# persons.collisions { |person| person.last_name }
#
#--
# Credit goes to Florian Gross
#++
def commonality( &block )
had_no_block = !block
block ||= lambda { |item| item }
result = Hash.new { |hash, key| hash[key] = Array.new }
self.each do |item|
key = block.call(item)
result[key] << item
end
result.reject! do |key, values|
values.size <= 1
end
#return had_no_block ? result.values.flatten : result
return result
end
end
# _____ _
# |_ _|__ ___| |_
# | |/ _ \/ __| __|
# | | __/\__ \ |_
# |_|\___||___/\__|
#
=begin test
require 'test/unit'
class TCEnumerable < Test::Unit::TestCase
def test_commonality
a = [1,2,2,3,3,3]
r = { 2 => [2,2], 3 => [3,3,3] }
assert_equal( r, a.commonality )
a = [1,2,2,3,3,3]
r = {false=>[1, 2, 2], true=>[3, 3, 3]}
assert_equal( r, a.commonality { |x| x > 2 } )
end
end
=end
Version data entries
26 entries across 26 versions & 1 rubygems