VB.NET Language in a Nutshell, Second Edition

Polymorphism and Overloading

Fortunately, we don’t need to go into the details of polymorphism and overloading, which is just as well, because they tend to be both confusing and ambiguous. For instance, some computer scientists say that overloading is a form of polymorphism, whereas others say it is not. We will discuss only those issues that are directly relevant to the .NET Framework.

Overloading

Overloading refers to an item being used in more than one way. Operator names are often overloaded. For instance, the plus sign (+) refers to addition of integers, addition of singles, addition of doubles, and concatenation of strings. Thus, the plus symbol (+) is overloaded. It’s a good thing, too; otherwise, we would need separate symbols for adding integers, singles, and doubles.

Function names can also be overloaded. For instance, the absolute value function, Abs, can take an integer parameter, a single parameter, or a double parameter. Because the name Abs represents several different functions, it is overloaded. In fact, if you look at the documentation for the Abs member of the Math class (in the System namespace of the Framework Class Library), you will find the following declarations, showing the different functions using the Abs name:

Overloads Public Shared Function Abs(Decimal) As Decimal Overloads Public Shared Function Abs(Double) As Double Overloads Public Shared Function Abs(Integer) As Short Overloads Public Shared Function Abs(Integer) As Integer Overloads Public Shared ...