70 lines
2.1 KiB
Ruby
70 lines
2.1 KiB
Ruby
module Enumerable
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# Ruby 1.8.7 introduces group_by, but the result isn't ordered. Override it.
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remove_method(:group_by) if [].respond_to?(:group_by) && RUBY_VERSION < '1.9'
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# Collect an enumerable into sets, grouped by the result of a block. Useful,
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# for example, for grouping records by date.
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#
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# Example:
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#
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# latest_transcripts.group_by(&:day).each do |day, transcripts|
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# p "#{day} -> #{transcripts.map(&:class).join(', ')}"
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# end
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# "2006-03-01 -> Transcript"
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# "2006-02-28 -> Transcript"
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# "2006-02-27 -> Transcript, Transcript"
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# "2006-02-26 -> Transcript, Transcript"
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# "2006-02-25 -> Transcript"
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# "2006-02-24 -> Transcript, Transcript"
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# "2006-02-23 -> Transcript"
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def group_by
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inject ActiveSupport::OrderedHash.new do |grouped, element|
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(grouped[yield(element)] ||= []) << element
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grouped
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end
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end unless [].respond_to?(:group_by)
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# Calculates a sum from the elements. Examples:
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#
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# payments.sum { |p| p.price * p.tax_rate }
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# payments.sum(&:price)
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#
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# The latter is a shortcut for:
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#
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# payments.inject { |sum, p| sum + p.price }
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#
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# It can also calculate the sum without the use of a block.
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#
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# [5, 15, 10].sum # => 30
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# ["foo", "bar"].sum # => "foobar"
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# [[1, 2], [3, 1, 5]].sum => [1, 2, 3, 1, 5]
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#
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# The default sum of an empty list is zero. You can override this default:
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#
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# [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)
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#
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def sum(identity = 0, &block)
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return identity unless size > 0
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if block_given?
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map(&block).sum
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else
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inject { |sum, element| sum + element }
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end
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end
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# Convert an enumerable to a hash. Examples:
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#
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# people.index_by(&:login)
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# => { "nextangle" => <Person ...>, "chade-" => <Person ...>, ...}
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# people.index_by { |person| "#{person.first_name} #{person.last_name}" }
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# => { "Chade- Fowlersburg-e" => <Person ...>, "David Heinemeier Hansson" => <Person ...>, ...}
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#
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def index_by
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inject({}) do |accum, elem|
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accum[yield(elem)] = elem
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accum
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end
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end
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end
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