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70 lines
2.3 KiB
Ruby
70 lines
2.3 KiB
Ruby
require_relative '../../spec_helper'
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require 'bigdecimal'
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describe "BigDecimal#sub" do
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before :each do
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@one = BigDecimal("1")
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@zero = BigDecimal("0")
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@two = BigDecimal("2")
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@three = BigDecimal("3")
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@nan = BigDecimal("NaN")
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@infinity = BigDecimal("Infinity")
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@infinity_minus = BigDecimal("-Infinity")
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@one_minus = BigDecimal("-1")
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@frac_1 = BigDecimal("1E-99999")
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@frac_2 = BigDecimal("0.9E-99999")
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@frac_3 = BigDecimal("12345E10")
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@frac_4 = BigDecimal("98765E10")
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end
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it "returns a - b with given precision" do
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# documentation states, that precision is optional
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# but implementation raises ArgumentError if not given.
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@two.sub(@one, 1).should == @one
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@one.sub(@two, 1).should == @one_minus
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@one.sub(@one_minus, 1).should == @two
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@frac_2.sub(@frac_1, 1000000).should == BigDecimal("-0.1E-99999")
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@frac_2.sub(@frac_1, 1).should == BigDecimal("-0.1E-99999")
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# the above two examples puzzle me.
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in_arow_one = BigDecimal("1.23456789")
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in_arow_two = BigDecimal("1.2345678")
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in_arow_one.sub(in_arow_two, 10).should == BigDecimal("0.9E-7")
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@two.sub(@two,1).should == @zero
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@frac_1.sub(@frac_1, 1000000).should == @zero
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end
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describe "with Object" do
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it "tries to coerce the other operand to self" do
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object = mock("Object")
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object.should_receive(:coerce).with(@frac_3).and_return([@frac_3, @frac_4])
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@frac_3.sub(object, 1).should == BigDecimal("-0.9E15")
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end
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end
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describe "with Rational" do
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it "produces a BigDecimal" do
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(@three - Rational(500, 2)).should == BigDecimal('-0.247e3')
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end
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end
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it "returns NaN if NaN is involved" do
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@one.sub(@nan, 1).nan?.should == true
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@nan.sub(@one, 1).nan?.should == true
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end
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it "returns NaN if both values are infinite with the same signs" do
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@infinity.sub(@infinity, 1).nan?.should == true
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@infinity_minus.sub(@infinity_minus, 1).nan?.should == true
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end
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it "returns Infinity or -Infinity if these are involved" do
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@infinity.sub(@infinity_minus, 1).should == @infinity
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@infinity_minus.sub(@infinity, 1).should == @infinity_minus
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@zero.sub(@infinity, 1).should == @infinity_minus
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@frac_2.sub( @infinity, 1).should == @infinity_minus
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@two.sub(@infinity, 1).should == @infinity_minus
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end
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end
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