Operators are Functions

1.1 Operators are Functions

Operators are Functions

Each operator is actually a shorthand for a function named operator? where the ? is replaced by the actual operator symbol.
The function takes the same number and type of parameters as does the operator
The compiler translates the infix expressions into the equivalent function calls

Examples: operators as functions

If you write a + b*(-c), that’s actually just a shorthand for







operator
+(
a
, 
operator
*
(
b
, 
operator
-
(
c
)))

and if you write







testValue 
= 
(
x 
<= 
y 
) ;

that’s actually a shorthand for







operator
=(
testValue
, 
operator
<=(
x
, 
y 
) ;

Declaring Operators

Understanding that shorthand, we can declare our own operators by giving the appropriate operator function name:

class BidCollection {
          ⋮
  void addInTimeOrder (const Bid& value);
  //  Adds this bid into a position such that
  //   all bids are ordered by the time the bid was placed
  //Pre: getSize() <</span> getMaxSize()

  void operator+= (const Bid& value)
           {addInTimeOrder(value);}
          ⋮

Then







bids
.
addInTimeOrder
(
b 
) ;

and







bids 
+= 
b
;

would do the same thing

Keep it Natural

It’s easy to abuse operator overloading and simply make things confusing.
- E.g., Don’t use operator+ unless your class really does something "addition-like"
  - string concatenation

Most Commonly Overloaded Operators

There are, however, 3 groups of operators that are very commonly overloaded

I/O operators << >>
Comparison operators < ==
The assignment operator =