Exercises

In the following exercises, you will use ScalaSTM to implement various transactional programming abstractions. In most cases, their implementation will closely resemble a sequential implementation, while using transactions. In some cases, you might need to consult external literature or ScalaSTM documentation to correctly solve the exercise.

1. Implement the transactional pair abstraction, represented with the TPair class:

           class TPair[P, Q](pinit: P, qinit: Q) { 
             def first(implicit txn: InTxn): P = ??? 
             def first_=(x: P)(implicit txn: InTxn): P = ??? 
             def second(implicit txn: InTxn): Q = ??? 
             def second_=(x: Q)(implicit txn: InTxn): Q = ??? 
             def swap()(implicit e: P =:= Q, txn: InTxn): Unit = ??? 
           } 
   

   In addition to getters and setters for the two fields, the transactional pair defines the swap method that swaps the fields, and can only be called if types P and Q are the same.

2. Use ScalaSTM to implement the mutable...