Exercises

1. Design a program that calculates all the prime numbers up to 100 by eliminating all the numbers divisible by 2, 3, 5 and 7. Create an abstract class Sieve with one pure virtual method NextNumber. Implement a SourceSieve that simply iterates over all numbers from 1 to 100 in order. Implement Sieve2 that takes a reference to a Sieve in its constructor, and when asked to give the next number, keeps retrieving numbers from its child sieve until it finds one that is not divisible by 2 and returns it. Do the same for 3, 5 and 7. Create all these Sieves as local objects in main, chain them, and print all the numbers returned by the top Sieve. What order of Sieves is best?
2. Create an abstract class Command with two pure virtual methods Execute and Undo. Create command classes for our stack-based calculator, corresponding to all possible calculator inputs. For every user input construct a corresponding Command object, Execute it and push it on a two-deep stack of Command s. Add the ‘u’ (undo ) command to the calculator. The u-command pops the last Command from the command stack and calls its virtual method Undo.