  
  [1X24. Pseudo lists[0X
  
      | [10X Add(L,x)[0X Let L be a pseudo list of length n, and x an object compatible with the entries in L. If x is not in L then this operation converts L into a pseudo list of length n+1 by adding x as the final entry. If x is in L the operation has no effect on L. | 
      | [10X Append(L,K)[0X Let L be a pseudo list and K a list whose objects are compatible with those in L. This operation applies Add(L,x) for each x in K.                                                                                                                 | 
      | [10X ListToPseudoList(L)[0X Inputs a list L and returns the pseudo list representation of L.                                                                                                                                                                           | 
  
