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Problem Solutions




Thinking in C++
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Solutions to selected exercises can be found in the electronic document The Thinking in C++ Annotated Solution Guide, available for a small fee from

  1. Create a simple class with an overloaded operator++. Try calling this operator in both pre- and postfix form and see what kind of compiler warning you get.
  2. Create a simple class containing an int and overload the operator+ as a member function. Also provide a print( ) member function that takes an ostream& as an argument and prints to that ostream&. Test your class to show that it works correctly.
  3. Add a binary operator- to Exercise 2 as a member function. Demonstrate that you can use your objects in complex expressions like
    a + b – c.
  4. Add an operator++ and operator-- to Exercise 2, both the prefix and the postfix versions, such that they return the incremented or decremented object. Make sure that the postfix versions return the correct value.
  5. Modify the increment and decrement operators in Exercise 4 so that the prefix versions are return a non-const reference and the postfix versions are return a const object. Show that they work correctly and explain why this would be done in practice.
  6. Change the print( ) function in Exercise 2 so that it is the overloaded operator<< as in IostreamOperatorOverloading.cpp.
  7. Modify Exercise 3 so that the operator+ and operator- are non-member functions. Demonstrate that they still work correctly.
  8. Add the unary operator- to Exercise 2 and demonstrate that it works correctly.
  9. Create a class that contains a single private char. Overload the iostream operators << and >> (as in IostreamOperatorOverloading.cpp) and test them. You can test them with fstreams, stringstreams, and cin and cout.
  10. Determine the dummy constant value that your compiler passes for postfix operator++ and operator--.
  11. Write a Number class that holds a double, and add overloaded operators for +, –, *, /, and assignment. Choose the return values for these functions so that expressions can be chained together, and for efficiency. Write an automatic type conversion operator intdouble( ).
  12. Modify Exercise 11 so that the return value optimization is used, if you have not already done so.
  13. Create a class that contains a pointer, and demonstrate that if you allow the compiler to synthesize the operator= the result of using that operator will be pointers that are aliased to the same storage. Now fix the problem by defining your own operator= and demonstrate that it corrects the aliasing. Make sure you check for self-assignment and handle that case properly.
  14. Write a class called Bird that contains a string member and a static int. In the default constructor, use the int to automatically generate an identifier that you build in the string, along with the name of the class (Bird #1, Bird #2, etc.). Add an operator<< for ostreams to print out the Bird objects. Write an assignment operator= and a copy-constructor. In main( ), verify that everything works correctly.
  15. Write a class called BirdHouse that contains an object, a pointer and a reference for class Bird from Exercise 14. The constructor should take the three Birds as arguments. Add an operator<< for ostreams for BirdHouse. Write anDisallow the assignment operator= and a copy-constructor. In main( ), verify that everything works correctly. Make sure that you can chain assignments for BirdHouse objects and build expressions involving multiple operators.
  16. Add an int data member to both Bird and BirdHouse in Exercise 15. Add member operators +, -, *, and / that use the int members to perform the operations on the respective members. Verify that these work.
  17. Repeat Exercise 16 using non-member operators.
  18. Add an operator-- to SmartPointer.cpp and NestedSmartPointer.cpp.
  19. Modify CopyingVsInitialization.cpp so that all of the constructors print a message that tells you what’s going on. Now verify that the two forms of calls to the copy-constructor (the assignment form and the parenthesized form) are equivalent.
  20. Attempt to create a non-member operator= for a class and see what kind of compiler message you get.
  21. Create a class with an copy-constructor assignment operator that has a second argument, a string that has a default value that says “CC op= call.” Create a function that takes assigns an object of your class by value to another one and show that your copy-constructorassignment operator is called correctly.
  22. In CopyingWithPointers.cpp, remove the operator= in DogHouse and show that the compiler-synthesized operator= correctly copies the string but simply aliases the Dog pointer.
  23. In ReferenceCounting.cpp, add a static int and an ordinary int as data members to both Dog and DogHouse. In all constructors for both classes, increment the static int and assign the result to the ordinary int to keep track of the number of objects that have been created. Make the necessary modifications so that all the printing statements will say the int identifiers of the objects involved.
  24. Create a class containing a string as a data member. Initialize the string in the constructor, but do not create a copy-constructor or operator=. Make a second class that has a member object of your first class; do not create a copy-constructor or operator= for this class either. Demonstrate that the copy-constructor and operator= are properly synthesized by the compiler.
  25. Combine the classes in OverloadingUnaryOperators.cpp and Integer.cpp.
  26. Modify PointerToMemberOperator.cpp by adding two new member functions to Dog that take no arguments and return void. Create and test an overloaded operator->* that works with your two new functions.
  27. Add an operator->* to NestedSmartPointer.cpp.
  28. Create two classes, Apple and Orange. In Apple, create a constructor that takes an Orange as an argument. Create a function that takes an Apple and call that function with an Orange to show that it works. Now make the Apple constructor explicit to demonstrate that the automatic type conversion is thus prevented. Modify the call to your function so that the conversion is made explicitly and thus succeeds.
  29. Add a global operator* to ReflexivityInOverloading.cpp and demonstrate that it is reflexive.
  30. Create two classes and create an operator+ and the conversion functions such that addition is reflexive for the two classes.
  31. Fix TypeConversionFanout.cpp by creating an explicit function to call to perform the type conversion, instead of one of the automatic conversion operators.
  32. Write simple code that uses the +, -, *, and / operators for doubles. Figure out how your compiler generates assembly code and look at the assembly language that’s generated to discover and explain what’s going on under the hood.

[49] Rob Murray, C++ Strategies & Tactics, Addison-Wesley, 1993, page 47.

Thinking in C++
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   Reproduced courtesy of Bruce Eckel, MindView, Inc. Design by Interspire