Typedef or Using

• This is section 10.2, the first part.
• Sometimes it is nice to provide a nickname for a type.
  • You might want to replace the type in the future with a different type.
  • You might want to form an abstraction.
  • You might want to make something that is long, or hard to type, easier to use.
• To do this:
  • C/C++ through 11 provide the typedef statement.
  • C++ 11 and beyond provide using
• Syntax
  • typedef existingType identifier
  • using identifier = existingType
• Example:

  • typedef unsigned int NumberT;
    using NumberT = unsignedInt;
            

• After the statement, the identifier now names a new type.
  • With either of the above statements, NumberT is now usable as a type.
• I like to use the format of functions for my type names.
  • But I append a T and the end.
  • So anything ending with a T is a type.
• See factorial.cpp
  • Note I use the typedef for two reasons here.
  • The flexibility to change the type.
  • I don't want to type unsigned long long everwhere.
• In most cases, the using versions seems to be preferred.