****************************************
mailbox_assignment2.sv
****************************************
include "transaction.sv";

program mailbox_assignment2;
// instatiating mailbox of of trasnsaction reference
  mailbox#(trasnsaction) myMailbox;

int num_trans = 10;

//like main in c
initial begin
     myMailbox = new();
     $display($time,"join started");
    fork
      producer();
      consumer();
    join
    $display($time,"join ended");
    #700
    //join none
    $display($time,"join none start");
    fork
       producer();
       consumer();
    join_none
    $display($time,"join none ended");

    #1700;
    $display($time,"join any start");
    fork
      producer();
      consumer();
    join_any
    $display($time,"join any ended");
    #3700

    $finish();

end

task producer();
    trasnsaction tr;

    //using repeat instead of while
    repeat(10)
    begin
        #2
        tr = new();
        // using $random() to simplify transaction
        tr.data = $urandom;
        tr.compute_ref();
        myMailbox.put(tr);
        $display("@%0t:producer:%d!",$time,tr.data);
    end
endtask

task consumer();
    trasnsaction tr;
    repeat(10)
    begin
        #20
     //   tr = new();
        if(myMailbox.num() > 0) begin
            myMailbox.get(tr);
            $display("@%0t:consumer:%d!",$time,tr.data);
        end
        else begin #2; end
    end
endtask
endprogram

*********************************************
do file
********************************************
vlog -reportprogress 300 -work work transaction.sv
vlog -reportprogress 300 -work work mailbox_assignment2.sv
vsim work.mailbox_assignment2
run -all

********************************************
transaction.sv
********************************************
class trasnsaction;
rand bit [3:0] data;
logic [7:0] reference;
static bit [7:0] counter_value;
function new;
counter_value = 0;
endfunction
function [7:0] compute_ref;
reference = counter_value+data;
counter_value = counter_value+data;
endfunction
endclass