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module Enumerable
# See Enumerable#partition for the background. #partition_by is best
# explained by example.
#
# (1..5).partition_by { |n| n % 3 }
# #=> { 0 => [3], 1 => [1, 4], 2 => [2,5] }
#
# ["I had", 1, "dollar and", 50, "cents"].partition_by { |e| e.class }
# #=> { String => ["I had","dollar and","cents"], Fixnum => [1,50] }
#
# #partition_by is used to group items in a collection by something they
# have in common. The common factor is the key in the resulting hash, the
# array of like elements is the value.
#--
# Credit goes to Gavin Sinclair.
#++
def partition_by #:yield:
result = {}
self.each do |e|
value = yield e
(result[value] ||= []) << e
end
result
end
end
# _____ _
# |_ _|__ ___| |_
# | |/ _ \/ __| __|
# | | __/\__ \ |_
# |_|\___||___/\__|
#
=begin test
require 'test/unit'
class TCEnumerable < Test::Unit::TestCase
def test_partition_by
x = (1..5).partition_by{ |n| n % 3 }
o = { 0 => [3], 1 => [1, 4], 2 => [2,5] }
assert_equal( o, x )
x = ["I had", 1, "dollar and", 50, "cents"].partition_by { |e| e.class }
o = { String => ["I had","dollar and","cents"], Fixnum => [1,50] }
assert_equal( o, x )
end
end
=end
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20 entries across 20 versions & 1 rubygems