Arithmetic circuits- 4bit adder

4 BIT ADDER

module adder4bit(carry,sum,a,b);
output [3:0]sum;
output carry ;
input [3:0]a,b;
reg [3:0]sum;
reg carry;
reg [4:0]tmp;
always @(a,b)
begin
assign tmp=a+b;
assign sum=tmp[3:0];
assign carry=tmp[4];
end
endmodule