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require File.dirname(__FILE__) + '/../../spec_helper'
require 'bigdecimal'
describe "BigDecimal#-" do
before(:each) do
@one = BigDecimal("1")
@zero = BigDecimal("0")
@two = BigDecimal("2")
@nan = BigDecimal("NaN")
@infinity = BigDecimal("Infinity")
@infinity_minus = BigDecimal("-Infinity")
@one_minus = BigDecimal("-1")
@frac_1 = BigDecimal("1E-99999")
@frac_2 = BigDecimal("0.9E-99999")
end
it "returns a - b" do
(@two - @one).should == @one
(@one - @two).should == @one_minus
(@one - @one_minus).should == @two
(@frac_2 - @frac_1).should == BigDecimal("-0.1E-99999")
(@two - @two).should == @zero
(@frac_1 - @frac_1).should == @zero
(BigDecimal('1.23456789') - BigDecimal('1.2')).should == BigDecimal("0.03456789")
end
it "returns NaN if NaN is involved" do
(@one - @nan).nan?.should == true
(@nan - @one).nan?.should == true
(@nan - @nan).nan?.should == true
(@nan - @infinity).nan?.should == true
(@nan - @infinity_minus).nan?.should == true
(@infinity - @nan).nan?.should == true
(@infinity_minus - @nan).nan?.should == true
end
it "returns NaN both operands are infinite with the same sign" do
(@infinity - @infinity).nan?.should == true
(@infinity_minus - @infinity_minus).nan?.should == true
end
it "returns Infinity or -Infinity if these are involved" do
(@infinity - @infinity_minus).should == @infinity
(@infinity_minus - @infinity).should == @infinity_minus
(@infinity - @zero).should == @infinity
(@infinity - @frac_2).should == @infinity
(@infinity - @two).should == @infinity
(@infinity - @one_minus).should == @infinity
(@zero - @infinity).should == @infinity_minus
(@frac_2 - @infinity).should == @infinity_minus
(@two - @infinity).should == @infinity_minus
(@one_minus - @infinity).should == @infinity_minus
end
end
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