yosys/tests/hana/test_simulation_sop_basic_11_test.v

module test(input [3:0] in, input [1:0] select, output reg out);

always @( in or select)
    case (select)
	    0: out = in[0];
	    1: out = in[1];
	    2: out = in[2];
	    3: out = in[3];
	endcase
endmodule