mirror of
https://github.com/ruby/ruby.git
synced 2022-11-09 12:17:21 -05:00
69 lines
2 KiB
Ruby
69 lines
2 KiB
Ruby
require_relative '../../spec_helper'
|
|
|
|
describe "Math.gamma" do
|
|
it "returns +infinity given 0" do
|
|
Math.gamma(0).should == Float::INFINITY
|
|
end
|
|
|
|
platform_is_not :windows do
|
|
# https://bugs.ruby-lang.org/issues/12249
|
|
it "returns -infinity given -0.0" do
|
|
Math.gamma(-0.0).should == -Float::INFINITY
|
|
end
|
|
end
|
|
|
|
it "returns Math.sqrt(Math::PI) given 0.5" do
|
|
Math.gamma(0.5).should be_close(Math.sqrt(Math::PI), TOLERANCE)
|
|
end
|
|
|
|
# stop at n == 23 because 23! cannot be exactly represented by IEEE 754 double
|
|
it "returns exactly (n-1)! given n for n between 2 and 23" do
|
|
fact = 1
|
|
2.upto(23) do |n|
|
|
fact *= (n - 1)
|
|
Math.gamma(n).should == fact
|
|
end
|
|
end
|
|
|
|
it "returns approximately (n-1)! given n for n between 24 and 30" do
|
|
fact2 = 1124000727777607680000 # 22!
|
|
24.upto(30) do |n|
|
|
fact2 *= n - 1
|
|
# compare only the first 12 places, tolerate the rest
|
|
Math.gamma(n).should be_close(fact2, fact2.to_s[12..-1].to_i)
|
|
end
|
|
end
|
|
|
|
it "returns good numerical approximation for gamma(3.2)" do
|
|
Math.gamma(3.2).should be_close(2.423965, TOLERANCE)
|
|
end
|
|
|
|
it "returns good numerical approximation for gamma(-2.15)" do
|
|
Math.gamma(-2.15).should be_close(-2.999619, TOLERANCE)
|
|
end
|
|
|
|
it "returns good numerical approximation for gamma(0.00001)" do
|
|
Math.gamma(0.00001).should be_close(99999.422794, TOLERANCE)
|
|
end
|
|
|
|
it "returns good numerical approximation for gamma(-0.00001)" do
|
|
Math.gamma(-0.00001).should be_close(-100000.577225, TOLERANCE)
|
|
end
|
|
|
|
it "raises Math::DomainError given -1" do
|
|
-> { Math.gamma(-1) }.should raise_error(Math::DomainError)
|
|
end
|
|
|
|
# See https://bugs.ruby-lang.org/issues/10642
|
|
it "returns +infinity given +infinity" do
|
|
Math.gamma(infinity_value).infinite?.should == 1
|
|
end
|
|
|
|
it "raises Math::DomainError given negative infinity" do
|
|
-> { Math.gamma(-Float::INFINITY) }.should raise_error(Math::DomainError)
|
|
end
|
|
|
|
it "returns NaN given NaN" do
|
|
Math.gamma(nan_value).nan?.should be_true
|
|
end
|
|
end
|