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71 lines
2.2 KiB
Ruby
71 lines
2.2 KiB
Ruby
require_relative '../../spec_helper'
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describe "Array#sum" do
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it "returns the sum of elements" do
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[1, 2, 3].sum.should == 6
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end
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it "applies a block to each element before adding if it's given" do
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[1, 2, 3].sum { |i| i * 10 }.should == 60
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end
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# https://bugs.ruby-lang.org/issues/12217
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# https://github.com/ruby/ruby/blob/master/doc/ChangeLog-2.4.0#L6208-L6214
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it "uses Kahan's compensated summation algorithm for precise sum of float numbers" do
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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]
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naive_sum = floats.reduce { |sum, e| sum + e }
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naive_sum.should == 50.00000000000001
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floats.sum.should == 50.0
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end
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it "handles infinite values and NaN" do
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[1.0, Float::INFINITY].sum.should == Float::INFINITY
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[1.0, -Float::INFINITY].sum.should == -Float::INFINITY
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[1.0, Float::NAN].sum.should.nan?
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[Float::INFINITY, 1.0].sum.should == Float::INFINITY
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[-Float::INFINITY, 1.0].sum.should == -Float::INFINITY
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[Float::NAN, 1.0].sum.should.nan?
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[Float::NAN, Float::INFINITY].sum.should.nan?
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[Float::INFINITY, Float::NAN].sum.should.nan?
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[Float::INFINITY, -Float::INFINITY].sum.should.nan?
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[-Float::INFINITY, Float::INFINITY].sum.should.nan?
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[Float::INFINITY, Float::INFINITY].sum.should == Float::INFINITY
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[-Float::INFINITY, -Float::INFINITY].sum.should == -Float::INFINITY
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[Float::NAN, Float::NAN].sum.should.nan?
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end
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it "returns init value if array is empty" do
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[].sum(-1).should == -1
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end
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it "returns 0 if array is empty and init is omitted" do
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[].sum.should == 0
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end
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it "adds init value to the sum of elements" do
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[1, 2, 3].sum(10).should == 16
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end
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it "can be used for non-numeric objects by providing init value" do
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["a", "b", "c"].sum("").should == "abc"
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end
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it 'raises TypeError if any element are not numeric' do
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-> { ["a"].sum }.should raise_error(TypeError)
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end
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it 'raises TypeError if any element cannot be added to init value' do
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-> { [1].sum([]) }.should raise_error(TypeError)
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end
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it "calls + to sum the elements" do
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a = mock("a")
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b = mock("b")
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a.should_receive(:+).with(b).and_return(42)
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[b].sum(a).should == 42
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end
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end
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