DET

note
    description: "ALI application root class"
    date: "$Date$"
    revision: "$Revision$"

class
    APPLICATION

inherit
    ARGUMENTS_32

create
    make

feature {NONE} -- Initialization

    make
        local
            matrix : ARRAY [ARRAY[INTEGER]]
            arr: ARRAY[INTEGER]
            i: INTEGER
            j: INTEGER
            -- Run application.
        do
            --create matrix.make_filled ( create {ARRAY[INTEGER]}.make_filled (1, 1, 3) , 1, 3)
            create matrix.make_empty
            from i:=1 until i>3 loop
                create arr.make_empty
                from j:=1 until j>3 loop
                    arr.force (1 ,j)
                    j:= j+1
                end
                matrix.force (arr, i)
                i:= i + 1
            end
            matrix[1][1]:= 5
            matrix[2][2]:= 3
            print (det(matrix))
        end
    det(m: ARRAY[ARRAY[INTEGER]]): INTEGER
            require
                condition: m.count=(m[1].count)
            local
                i: INTEGER
                j: INTEGER
                k: INTEGER
                l: INTEGER
                a: INTEGER
                n: INTEGER
                m3: ARRAY[ARRAY[INTEGER]]
            do
                n:= m.count
                if n=1 then
                    a:=m[1][1]
                    print (m.count.out+"%N")
                else
                    a:=0
                    print (m.count.out+"%N")
                    create m3.make_empty
                    from i:=1 until i>n-1 loop
                        m3.force( create {ARRAY[INTEGER]}.make_filled (0, 1, n-1), i)
                        i:=i+1
                    end
                    from j:=1 until j>n loop

                        from k:=1 until k>n-1 loop
                            from l:=1 until l>j-1 loop
                                m3[k][l]:=m[k+1][l]
                                l:=l+1
                                --print (m3.count.out + "%N")
                            end
                            k:=k+1
                        end
                        from k:=1 until k>n-1 loop
                            from l:=j until l>n-1 loop
                                m3[k][l]:=m[k+1][l+1]
                                l:=l+1
                                --print (m3.count.out + "%N")
                            end
                            k:=k+1
                        end
                        if m.count = 2 then
                            print ( "%N" + m[1][1].out + m[1][2].out + m[2][1].out + m[2][2].out + "%N"  )
                        end
                        if j\\2=1 then
                            a:= a+m[1][j]*det(m3)
                        else
                            a:=a-m[1][j]*det(m3)
                        end
                        j:=j+1
                    end
                end
                Result:=a
            end

end