// Half Adder primitive
module half_adder (
input a, b,
output sum, carry
);
assign{carry,sum} = a + b;
endmodule
// Full Adder using 2 Half Adders
module full_adder_struct (
input a, b, cin,
output sum, cout
);
wire sum_tmp, c_tmp, c1_tmp;
half_adder adder1 (.a(a), .b(b), .sum(sum_tmp), .carry(c_tmp));
half_adder adder2 (.a(sum_tmp), .b(cin), .sum(sum), .carry(c1_tmp));
assign cout = c1_tmp | c_tmp;
endmodule