require_relative '../../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).should.nan?

(@nan - @one).should.nan?

(@nan - @nan).should.nan?

(@nan - @infinity).should.nan?

(@nan - @infinity_minus).should.nan?

(@infinity - @nan).should.nan?

(@infinity_minus - @nan).should.nan?

end

it "returns NaN both operands are infinite with the same sign" do

(@infinity - @infinity).should.nan?

(@infinity_minus - @infinity_minus).should.nan?

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

describe "with Object" do

it "tries to coerce the other operand to self" do

object = mock("Object")

object.should_receive(:coerce).with(@one).and_return([@one, BigDecimal("42")])

(@one - object).should == BigDecimal("-41")

end

end

end