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* Other ruby implementations use the spec/ruby directory. [Misc #13792] [ruby-core:82287] git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59979 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
69 lines
2 KiB
Ruby
69 lines
2 KiB
Ruby
require File.expand_path('../../../spec_helper', __FILE__)
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describe "Math.gamma" do
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it "returns +infinity given 0" do
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Math.gamma(0).should == Float::INFINITY
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end
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platform_is_not :windows do
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# https://bugs.ruby-lang.org/issues/12249
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it "returns -infinity given -0.0" do
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Math.gamma(-0.0).should == -Float::INFINITY
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end
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end
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it "returns Math.sqrt(Math::PI) given 0.5" do
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Math.gamma(0.5).should be_close(Math.sqrt(Math::PI), TOLERANCE)
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end
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# stop at n == 23 because 23! cannot be exactly represented by IEEE 754 double
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it "returns exactly (n-1)! given n for n between 2 and 23" do
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fact = 1
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2.upto(23) do |n|
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fact *= (n - 1)
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Math.gamma(n).should == fact
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end
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end
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it "returns approximately (n-1)! given n for n between 24 and 30" do
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fact2 = 1124000727777607680000 # 22!
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24.upto(30) do |n|
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fact2 *= n - 1
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# compare only the first 12 places, tolerate the rest
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Math.gamma(n).should be_close(fact2, fact2.to_s[12..-1].to_i)
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end
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end
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it "returns good numerical approximation for gamma(3.2)" do
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Math.gamma(3.2).should be_close(2.423965, TOLERANCE)
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end
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it "returns good numerical approximation for gamma(-2.15)" do
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Math.gamma(-2.15).should be_close(-2.999619, TOLERANCE)
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end
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it "returns good numerical approximation for gamma(0.00001)" do
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Math.gamma(0.00001).should be_close(99999.422794, TOLERANCE)
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end
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it "returns good numerical approximation for gamma(-0.00001)" do
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Math.gamma(-0.00001).should be_close(-100000.577225, TOLERANCE)
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end
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it "raises Math::DomainError given -1" do
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lambda { Math.gamma(-1) }.should raise_error(Math::DomainError)
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end
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# See https://bugs.ruby-lang.org/issues/10642
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it "returns +infinity given +infinity" do
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Math.gamma(infinity_value).infinite?.should == 1
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end
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it "raises Math::DomainError given negative infinity" do
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lambda { Math.gamma(-Float::INFINITY) }.should raise_error(Math::DomainError)
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end
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it "returns NaN given NaN" do
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Math.gamma(nan_value).nan?.should be_true
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end
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end
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