module carry_lookahead_adder(a,b,carryin,sum,carryout);
	input [15:0] a, b; /* add these together */
	input carryin;
	output [15:0] sum; /* result */
	output carryout;
	wire [16:1] carry; /* intermediate carries */

	assign carryout = carry[16]; /* for simplicity */
	/* build the carry-lookahead units */
	carry_block b0(a[3:0],b[3:0],carryin,carry[4:1]);
	carry_block b1(a[7:4],b[7:4],carry[4],carry[8:5]);
	carry_block b2(a[11:8],b[11:8],carry[8],carry[12:9]);
	carry_block b3(a[15:12],b[15:12],carry[12],carry[16:13]);
	/* build the sum */
	sum  a0(a[0],b[0],carryin,sum[0]);
	sum  a1(a[1],b[1],carry[1],sum[1]);
	sum  a2(a[2],b[2],carry[2],sum[2]);
	sum  a3(a[3],b[3],carry[3],sum[3]);
	sum  a4(a[4],b[4],carry[4],sum[4]);
	sum  a5(a[5],b[5],carry[5],sum[5]);	
	sum  a6(a[6],b[6],carry[6],sum[6]);
	sum  a7(a[7],b[7],carry[7],sum[7]);
	sum  a8(a[8],b[8],carry[8],sum[8]);
	sum  a9(a[9],b[9],carry[9],sum[9]);
	sum a10(a[10],b[10],carry[10],sum[10]);
	sum a11(a[11],b[11],carry[11],sum[11]);
	sum a12(a[12],b[12],carry[12],sum[12]);
	sum a13(a[13],b[13],carry[13],sum[13]);
	sum a14(a[14],b[14],carry[14],sum[14]);	
	sum a15(a[15],b[15],carry[15],sum[15]);
endmodule