number of ones in array

Question

I am trying to count the number of ones in a 4-bit binary number in Verilog, but my output is unexpected. I\'ve tried several approaches; this is the one I think should work

Answer 1

First, you can't assign the variable twice.

Second, your range is off, 2 bits can only go from 0 to 3. You need a 3 bit output to count up to 4.

This is more like what you need:

module ones(
  output wire [2:0] one,
  input wire [3:0] in
);

assign one = in[3]+in[2]+in[1]+in[0] ;

endmodule