// Half Adder primitive
module half_adder (
input a, b,
output sum, carry
);
assign sum=a^b;
assign carry=a|b;
endmodule
// Full Adder using 2 Half Adders
module full_adder_struct (
input a, b, cin,
output sum, cout
);
assign sum=a^b^cin;
assign cout= a&b|b&cin|a&cin;
endmodule