require_relative '../../../spec_helper'

ruby_version_is ""..."3.1" do
  require 'matrix'

  describe "Matrix::LUPDecomposition#to_a" do
    before :each do
      @a = Matrix[[7, 8, 9], [14, 46, 51], [28, 82, 163]]
      @lu = Matrix::LUPDecomposition.new(@a)
      @to_a = @lu.to_a
      @l, @u, @p = @to_a
    end

    it "returns an array of three matrices" do
      @to_a.should be_kind_of(Array)
      @to_a.length.should == 3
      @to_a.each{|m| m.should be_kind_of(Matrix)}
    end

    it "returns [l, u, p] such that l*u == a*p" do
      (@l * @u).should == (@p * @a)
    end

    it "returns the right values for rectangular matrices" do
      [
        Matrix[[7, 8, 9], [14, 46, 51]],
        Matrix[[4, 11], [5, 8], [3, 4]],
      ].each do |a|
        l, u, p = Matrix::LUPDecomposition.new(a).to_a
        (l * u).should == (p * a)
      end
    end

    it "has other properties implied by the specs of #l, #u and #p"
  end
end