
One common place to see a replication operator is when sign-extending a
smaller number to a larger one, while preserving its signed value. This
is done by replicating the sign bit (the most significant bit) of the
smaller number to the left. For example, sign-extending 4'b0101 (5) to 8
bits results in 8'b00000101 (5), while sign-extending 4'b1101 (-3) to 8
bits results in 8'b11111101 (-3). Build a circuit that sign-extends an
8-bit number to 32 bits. This requires a concatenation of 24 copies of
the sign bit (i.e., replicate bit[7] 24 times) followed by the 8-bit
number itself.

module TopModule (
  input [7:0] in,
  output [31:0] out
);

