It’s easy to get the first cycle of random numbers by pushing values on a list in post_randomize() and adding a constraint that keeps the values in the list excluded from the next solution.

class A;

   rand mytype_t myvar;

   mytype_t list[$];

   constraint cycle { unique {myvar,list};}

   function void post_randomize;

     list.push_back(myvar); //storing each myvar into list[$]

   endfunction 

endclass

 

The real problem is knowing when to start the cycle over by clearing the list. If the exact number of possible values for myvar is known, you can add a pre_randomize() method that deletes the list when hitting that limit.

function void pre_randomize;

 if (list.size() == limit) 

   list = {}; //delete queue

endfunction

 

Otherwise you will have to check the result of calling randomize() and assume it fails because it has exhausted the list of values.