Enumeration Types

• Starting on page 467 of the book.
• A reference
• In our sample project, we have a die that can return multiple possibilities.
  • Yellow Sign
  • Tentacle
  • Elder Sign
  • Cthulhu
  • Eye
• How can we represent these in code?
  • Strings:
    • This is expandable.
    • Somewhat self documenting.
    • But there is the case problem (all lower, all upper, mixed)
    • And the spelling problem
    • And strings take a bit of space.
  • We could use consts

    • const int YELLOW_SIGN = 1;
      const int TENTACLE = 2;
      const int ELDER_SIGN = 3;
      const int CTHULHU = 4;
      const int EYE = 5; 

    • This is expandable.
    • This is somewhat self documenting.
    • It solves the size problem.
    • But there is nothing to keep this from happening:

    • const int CTHULHU = 4;
      const int EYE = 4; 

  • C has an enumeration or enumerated type.
    • They allow the user to define the domain of the type.
    • But the representation is integer.
    • The operations are integer.
    • Syntax

      • enum identifier {identifier[=const int expression], identifier, ...}
                    

    • Example:

      • enum ResultT {YELLOW_SIGN, TENTACLE, ELDER_SIGN, CTHULHU, EYE, UNKNOWN}; 

• Notice
  • Unless you force it, you can not duplicate the values.
  • The compiler now checks for spelling mistakes
  • This is easily expandable, just add another name.
  • This is the size of an int, so it is efficient
• Conventions
  • Please name any new types with Camel Case, ending with a T
  • Enumerators should be all upper case.
• Some observations
  • Generally I/O is bad, you need to write conversion routines.
  • Increment should be handled in a conversion routine.
    • C++ does not perform range checking.
    • And it is not happy with resType = resType + 1
      • A cast is required.
• Take a look at die.cpp