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require File.expand_path('../../../spec_helper', __FILE__)
describe "Float#prev_float" do
it "returns a float the smallest possible step smaller than the receiver" do
barely_negative = 0.0.prev_float
barely_negative.should == 0.0.prev_float
barely_negative.should < 0.0
barely_negative.should > barely_negative.prev_float
midpoint = barely_negative / 2
[0.0, barely_negative].should include midpoint
end
it "returns -Float::INFINITY for -Float::INFINITY" do
(-Float::INFINITY).prev_float.should == -Float::INFINITY
end
it "steps directly between MAX and INFINITY" do
Float::INFINITY.prev_float.should == Float::MAX
(-Float::MAX).prev_float.should == -Float::INFINITY
end
it "steps directly between 1.0 and 1.0 - EPSILON/2" do
1.0.prev_float.should == 1.0 - Float::EPSILON/2
end
it "steps directly between -1.0 and -1.0 - EPSILON" do
(-1.0).prev_float.should == -1.0 - Float::EPSILON
end
it "reverses the effect of next_float for all Floats except -INFINITY and -0.0" do
num = rand
num.next_float.prev_float.should == num
end
it "returns positive zero when stepping downward from just above zero" do
x = 0.0.next_float.prev_float
(1/x).should == Float::INFINITY
end
it "gives the same result for -0.0 as for +0.0" do
(0.0).prev_float.should == (-0.0).prev_float
end
it "returns NAN if NAN was the receiver" do
Float::NAN.prev_float.nan?.should == true
end
end
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