//2023-11-14 
//·ѡ if-else

`timescale 1ns/10ps
module fn_sw (
                    a,
                    b,
                    sel,
                    y
            );

input               a,b;
input[1:0]          sel;
output              y;

reg                 y;

always @(*) begin

    if(sel==00)
       y=a&b;
    else if(sel==01)
       y=a|b;
    else if(sel==10)
       y=a^b;
    else
       y=~(a^b);
    
end
    
endmodule


//-----------testbench-----------

module tb_fn_sw ();

reg[3:0]            sba;
wire                yy;

always #10          sba=sba+1;

initial begin
                    sba=4'b0000;
            #200    $stop;
end


fn_sw fn_sw (
                    .a(sba[0]),
                    .b(sba[1]),
                    .sel(sba[3:2]),
                    .y(yy)
            );
    
endmodule