combinational for-loop：255-bit population count

A "population count" circuit counts the number of '1's in an input vector. Build a population count circuit for a 255-bit input vector.

Popcount255 - HDLBits (01xz.net)

module top_module( 
    input [254:0] in,
    output [7:0] out );
 integer i;
    always @(*) begin
        out = 0;
        for(i=0;i<$bits(in);i=i+1) begin    // $bits（）为计算位宽函数
            if(in[i]) out = out+8'b1;  
        end
    end   

endmodule

 另一种写法：

module top_module( 
    input [254:0] in,
    output [7:0] out );
    integer i;
    integer temp;
    always @(*) begin
        out = 8'd0;
        for(i=0;i<255;i++) begin
            out = out + in[i];
        end
    end
endmodule

此题我理解为输入input每进来一个，output就加一个计数