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require_relative '../../spec_helper'
require_relative 'fixtures/classes'
describe 'Enumerable#sum' do
before :each do
@enum = Object.new.to_enum
class << @enum
def each
yield 0
yield(-1)
yield 2
yield 2/3r
end
end
end
it 'returns amount of the elements with taking an argument as the initial value' do
@enum.sum(10).should == 35/3r
end
it 'gives 0 as a default argument' do
@enum.sum.should == 5/3r
end
it 'takes a block to transform the elements' do
@enum.sum { |element| element * 2 }.should == 10/3r
end
# https://bugs.ruby-lang.org/issues/12217
# https://github.com/ruby/ruby/blob/master/doc/ChangeLog-2.4.0#L6208-L6214
it "uses Kahan's compensated summation algorithm for precise sum of float numbers" do
floats = [2.7800000000000002, 5.0, 2.5, 4.44, 3.89, 3.89, 4.44, 7.78, 5.0, 2.7800000000000002, 5.0, 2.5].to_enum
naive_sum = floats.reduce { |sum, e| sum + e }
naive_sum.should == 50.00000000000001
floats.sum.should == 50.0
end
end
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