CompE260

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Lecture 14

• CompE260

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Overloading

• Overloading allows the programmer to use the same
  name or symbol for different purposes.
• Things that can be overloaded included
• Operators (symbols) ,, -, , /, gt, lt, lt, gt,
  , , , , ,
• Method (function) names

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Operator Overloading

• C allows the programmer to define the meaning
  of an operator for a class. This is called
  overloading the operator.
• Example, if I define a Matrix class, then I will
  probably want to define Matrix operations such as
  addition, subtraction, etc. Operator overloading
  allows you to use a symbol such as as the name
  of a function.

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Operator Overloading II

• The compiler detects whether an operator is
  overloaded, the by looking for a function of the
  form
• return type operator symbol(ptype p1 )
• CplxNum operator(CplxNum A)
• Overloaded Operators may be either members of a
  class or not members of a class.

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Overloaded Operators that are Members of a class

• Prototype
• CplxNum CplxNumoperator(CplxNum Num)
• CplxNum CplxNumoperator(int real)
• CplxNum CplxNumoperator-(CplxNum Num)
• Usage
• CplxNum A, B, C
• Int real
• C A B is understood to mean C
  A.operator(B)
• C A real is understood to mean C
  A.operator(real)
• Where operator is the name of a function that is
  a member of the class CplxNum.

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Overloaded Operators that are Not Members of a
class

• Prototype
• CplxNum operator(CplxNum Num1, CplxNum Num2)
• Note 2 arguments NOT 1
• Usage
• CplxNum A, B, C
• C A B is understood to mean C operator(A,
  B)
• Where operator is the name of a function that is
  a NOT a member of the class CplxNum.
• Since the function operator is not a member of
  the class CplxNum, it does not have access to the
  private members of the class.

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Overloading of Class Methods

• A class is permitted to have multiple functions
  (methods) that share the same name. If this
  occurs, such methods are called overloaded.
• The compiler determines which function to
  actually call by looking at the combination of
  the
• Class Name
• Method Name
• Method Parameter List or Signature

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Assignment Operator

• When you use the assignment operator () with a
  class, the compiler will copy all the data
  members from the object on the right side of the
  operator to the object on the left side of the
  operator.
• After the assignment operation, the members of
  each object are the same!!
• The operator will NOT follow any references for
  dynamically assigned memory.
• You need to overload the operator to perform
  this action.

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this

• When a class method is called
• CplxNum A, B
• A.SetMagnitude(1)
• Calls the class method SetMagnitude with a
  parameter of 1 for the object A.
• B.SetMagnitude(1)
• Calls the class method SetMagnitude with a
  parameter of 1 for the object B.
• The compiler passes the method a pointer to the
  object for which the method was called.
• The SetMagnitude method has a pointer to the
  object A.
• The pointer is passed in a predefined location
  called this.
• The programmer can use the this pointer to access
  the objects data attributes or other functions by
  reference rather than value.
• this-gtvarA arg1