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require 'active_support/ordered_hash'
module Enumerable
# Ruby 1.8.7 introduces group_by, but the result isn't ordered. Override it.
remove_method(:group_by) if [].respond_to?(:group_by) && RUBY_VERSION < '1.9'
# Collect an enumerable into sets, grouped by the result of a block. Useful,
# for example, for grouping records by date.
#
# Example:
#
# latest_transcripts.group_by(&:day).each do |day, transcripts|
# p "#{day} -> #{transcripts.map(&:class).join(', ')}"
# end
# "2006-03-01 -> Transcript"
# "2006-02-28 -> Transcript"
# "2006-02-27 -> Transcript, Transcript"
# "2006-02-26 -> Transcript, Transcript"
# "2006-02-25 -> Transcript"
# "2006-02-24 -> Transcript, Transcript"
# "2006-02-23 -> Transcript"
def group_by
assoc = ActiveSupport::OrderedHash.new
each do |element|
key = yield(element)
if assoc.has_key?(key)
assoc[key] << element
else
assoc[key] = [element]
end
end
assoc
end unless [].respond_to?(:group_by)
# Calculates a sum from the elements. Examples:
#
# payments.sum { |p| p.price * p.tax_rate }
# payments.sum(&:price)
#
# The latter is a shortcut for:
#
# payments.inject(0) { |sum, p| sum + p.price }
#
# It can also calculate the sum without the use of a block.
#
# [5, 15, 10].sum # => 30
# ["foo", "bar"].sum # => "foobar"
# [[1, 2], [3, 1, 5]].sum => [1, 2, 3, 1, 5]
#
# The default sum of an empty list is zero. You can override this default:
#
# [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)
#
def sum(identity = 0, &block)
if block_given?
map(&block).sum(identity)
else
inject { |sum, element| sum + element } || identity
end
end
# Iterates over a collection, passing the current element *and* the
# +memo+ to the block. Handy for building up hashes or
# reducing collections down to one object. Examples:
#
# %w(foo bar).each_with_object({}) { |str, hsh| hsh[str] = str.upcase }
# # => {'foo' => 'FOO', 'bar' => 'BAR'}
#
# *Note* that you can't use immutable objects like numbers, true or false as
# the memo. You would think the following returns 120, but since the memo is
# never changed, it does not.
#
# (1..5).each_with_object(1) { |value, memo| memo *= value } # => 1
#
def each_with_object(memo, &block)
each do |element|
block.call(element, memo)
end
memo
end unless [].respond_to?(:each_with_object)
# Convert an enumerable to a hash. Examples:
#
# people.index_by(&:login)
# => { "nextangle" => <Person ...>, "chade-" => <Person ...>, ...}
# people.index_by { |person| "#{person.first_name} #{person.last_name}" }
# => { "Chade- Fowlersburg-e" => <Person ...>, "David Heinemeier Hansson" => <Person ...>, ...}
#
def index_by
inject({}) do |accum, elem|
accum[yield(elem)] = elem
accum
end
end
# Returns true if the collection has more than 1 element. Functionally equivalent to collection.size > 1.
# Works with a block too ala any?, so people.many? { |p| p.age > 26 } # => returns true if more than 1 person is over 26.
def many?(&block)
size = block_given? ? select(&block).size : self.size
size > 1
end
# The negative of the Enumerable#include?. Returns true if the collection does not include the object.
def exclude?(object)
!include?(object)
end
end
class Range #:nodoc:
# Optimize range sum to use arithmetic progression if a block is not given and
# we have a range of numeric values.
def sum(identity = 0)
return super if block_given? || !(first.instance_of?(Integer) && last.instance_of?(Integer))
actual_last = exclude_end? ? (last - 1) : last
(actual_last - first + 1) * (actual_last + first) / 2
end
end
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