66. Demultiplexer

module demux1to4 (
    input d,
    input [1:0] s,
    output reg [3:0] y
);
    integer i;

    always @* begin
        for (i=0; i<4; i=i+1)
            y[i] = (s==i) ? d : 1'b0;
    end
endmodule