Converting between Types

Sometimes all the operations "stay within a type".

• Casting
  • Traditionally, cast integers to floats, etc.
  • May need to convert between user-defined types
• Cast operator (conversion operator)
  • Convert from
    • One class to another
    • Class to built-in type (int, char, etc.)
  • Must be non-static member function; Cannot be friend
  • Do not specify return type; implicitly returns type to which you are converting
• Example
  • Prototype
    • A::operator char *() const;
    • Casts class A to a temporary char *
    • (char *)s calls s.operator char*()
  • Also, overloaded cast-operator functions can be defined for converting objects of user-defined types into built-in types or into objects of other user-defined types.
    • A::operator int() const;
    • A::operator OtherClass() const;
• Casting can prevent need for overloading
  • Suppose class String can be cast to char *
  • cout $<<$ s; // s is a String
    • Compiler implicitly converts s to char *
    • Do not have to overload $<<$