Enumerable#sum without blocks. Closes #5505. Don't assume 0 identity for sum.
git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4495 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
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@ -1,10 +1,11 @@
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*SVN*
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* Added Enumerable#sum for calculating a sum from the elements [DHH]. Examples:
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* Added Enumerable#sum for calculating a sum from the elements [DHH, jonathan@daikini.com]. Examples:
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[1, 2, 3].sum
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payments.sum { |p| p.price * p.tax_rate }
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payments.sum(&:price)
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This is instead of payments.inject(0) { |sum, p| sum + p.price }
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* Correct and clarify Array#to_sentence docs. #5458 [brad@madriska.com]
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@ -26,11 +26,18 @@ def group_by
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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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# This is instead of payments.inject(0) { |sum, p| sum + p.price }
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def sum
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inject(0) { |sum, element| sum + yield(element) }
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# This is instead of payments.inject { |sum, p| sum + p.price }
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#
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# Also calculates sums without the use of a block:
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# [5, 15, 10].sum # => 30
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def sum(&block)
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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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@ -45,4 +52,4 @@ def index_by
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end
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end
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end
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end
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@ -3,6 +3,9 @@
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require File.dirname(__FILE__) + '/../../lib/active_support/core_ext/enumerable'
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Payment = Struct.new(:price)
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class SummablePayment < Payment
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def +(p) self.class.new(price + p.price) end
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end
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class EnumerableTests < Test::Unit::TestCase
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def test_group_by
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@ -19,13 +22,31 @@ def test_group_by
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assert group.all? {|person| person.name == name}
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end
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end
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def test_sums
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assert_equal 30, [5, 15, 10].sum
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assert_equal 30, [5, 15, 10].sum { |i| i }
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assert_equal 'abc', %w(a b c).sum
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assert_equal 'abc', %w(a b c).sum { |i| i }
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payments = [ Payment.new(5), Payment.new(15), Payment.new(10) ]
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assert_equal 30, payments.sum(&:price)
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assert_equal 60, payments.sum { |p| p.price * 2 }
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payments = [ SummablePayment.new(5), SummablePayment.new(15) ]
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assert_equal SummablePayment.new(20), payments.sum
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assert_equal SummablePayment.new(20), payments.sum { |p| p }
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end
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def test_nil_sums
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assert_raise(TypeError) { [5, 15, nil].sum }
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payments = [ Payment.new(5), Payment.new(15), Payment.new(10), Payment.new(nil) ]
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assert_raise(TypeError) { payments.sum(&:price) }
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assert_equal 60, payments.sum { |p| p.price.to_i * 2 }
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end
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def test_index_by
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payments = [ Payment.new(5), Payment.new(15), Payment.new(10) ]
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assert_equal(
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@ -33,5 +54,4 @@ def test_index_by
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payments.index_by(&:price)
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)
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end
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end
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