69. Binary Subtractor

How do you plan to solve it?

/*Write your code here*/
module sub4_2c(
    input [3:0]a,b,
    output [3:0] diff,
    output bout
);
    assign diff = a + (~b + 1);
    assign bout = (a<b) ? 1'b1 : 1'b0;
endmodule