module Enumerable # Calculates a sum from the elements. # # 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(:+) || identity end end # Convert an enumerable to a hash. # # people.index_by(&:login) # => { "nextangle" => , "chade-" => , ...} # people.index_by { |person| "#{person.first_name} #{person.last_name}" } # => { "Chade- Fowlersburg-e" => , "David Heinemeier Hansson" => , ...} def index_by if block_given? Hash[map { |elem| [yield(elem), elem] }] else to_enum(:index_by) { size if respond_to?(:size) } end end # Returns +true+ if the enumerable has more than 1 element. Functionally # equivalent to enum.to_a.size > 1. Can be called with a block too, # much like any?, so people.many? { |p| p.age > 26 } returns +true+ # if more than one person is over 26. def many? cnt = 0 if block_given? any? do |element| cnt += 1 if yield element cnt > 1 end else any? { (cnt += 1) > 1 } end end # The negative of the Enumerable#include?. Returns +true+ if the # collection does not include the object. def exclude?(object) !include?(object) end # Returns a copy of the enumerable without the specified elements. # # ["David", "Rafael", "Aaron", "Todd"].without "Aaron", "Todd" # => ["David", "Rafael"] # # {foo: 1, bar: 2, baz: 3}.without :bar # => {foo: 1, baz: 3} def without(*elements) reject { |element| elements.include?(element) } end # Convert an enumerable to an array based on the given key. # # [{ name: "David" }, { name: "Rafael" }, { name: "Aaron" }].pluck(:name) # => ["David", "Rafael", "Aaron"] # # [{ id: 1, name: "David" }, { id: 2, name: "Rafael" }].pluck(:id, :name) # => [[1, "David"], [2, "Rafael"]] def pluck(*keys) if keys.many? map { |element| keys.map { |key| element[key] } } else map { |element| element[keys.first] } end 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) if block_given? || !(first.is_a?(Integer) && last.is_a?(Integer)) super else actual_last = exclude_end? ? (last - 1) : last if actual_last >= first (actual_last - first + 1) * (actual_last + first) / 2 else identity end end end end # Array#sum was added in Ruby 2.4 but it only works with Numeric elements. # # We tried shimming it to attempt the fast native method, rescue TypeError, # and fall back to the compatible implementation, but that's much slower than # just calling the compat method in the first place. if Array.instance_methods(false).include?(:sum) && !(%w[a].sum rescue false) class Array remove_method :sum def sum(*args) #:nodoc: # Use Enumerable#sum instead. super end end end