title: Declaring a constant with a parameterized width
body: <p>I want to declare constants with a parameterized width.
  For example, in this piece of code:</p>
  <pre><code>module mux2to1 #(parameter w = 4) (output [w-1:0] O, input [w-1:0] i0, i1, input Sel);
    assign O = (Sel)? i1 : i0;
  endmodule
  
  module M1 #(parameter n = 4) (input [n-1:0] A, input F, output [n+1:0] B);
    mux2to1#(n+2) mux (B, XXX, XXX, F);
  endmodule
  </code></pre>
  <p>In the XXXs, I would like to put all 1s for one of them, and for the other, I would like to put 0s followed by a single 1.</p>
  <p>How to do this?</p>