Just a few notes on object oriented programming.

Good article by Bjarne Stroustrup, inventor of C++ (pdf): What is ‘‘Object-Oriented Programming’’?

Summary

• Difference between enable and support
  • Enable: some feature is possible, but not easy (i.e., type checking in C)
  • Support: feature is made easy to use by language
  • Enabling doesn't really count -- support does
• Procedural programming
  • Decide which procedures you want; use the best algorithms you can find.
• Data hiding/modules
  • Decide which modules you want; partition the program so that data is hidden in modules.
  • Modules aren't as good as built-in types; must handle own memory management
• Data abstraction
  • Decide which types you want; provide a full set of operations for each type.
  • Like built-in types (called user defined types or abstract data types)
  • Problems with data abstraction
    • Inflexible: once class declared, does not change
• Object oriented
  • Decide which classes you want;
    provide a full set of operations for each class;
    make commonality explicit by using inheritance.
  • Don't pile everything into base class -- let derived classes extend it, provide specifics
  • Virtual functions: specify interface, but not implementation (derived class provides implementation)
  • OO programing usefulness varies
    • Good for graphics
    • Not great for arithmetic... if not useful, use data abstraction
  • Can be hard to extract commonality, depends on design of system
  • Notice that each class has functions that it defines, and act on it.
    • Different from making an outside function to modify an object
• Lesser details about OO and C++
• Initialization and construction in one step
  • Destructor to deallocate, if necessary (a non-trivial type)
  • Assignment, copy constructors, preventing assignment
• Template class
  • Family of types; create class to use any type
• Error handling (throwing/catching errors)
• Type conversions (implicit, explicit)
• Iterators
  • Loop through data structure without knowing its details
  • Iterator is a separate object, initialized with the object to iterate over
  • More general than having a "current" variable inside the class
• Class derivation (subclassing) important
  • Avoid having a type field (int type...) in the class, and then having to do a switch statement. Inelegant, not-scalable.
• Multiple inheritence
• Encapsulation: protected, friend