OpenOffice.org BASIC Guide.pdf - OpenOffice.org wiki

Working With Variables 8
Working With Variables
Implicit Variable Declaration
Basic languages are designed to be easy to use. As a result, OpenOffice.org Basic enables
the creation of a variable through simple usage and without an explicit declaration. In other
words, a variable exists from the moment that you include it in your code. Depending on the
variables that are already present, the following example declares up to three new
variables:
a = b + c
Declaring variables implicitly is not good programming practice because it can result in the
inadvertent introduction of a new variable through, for example, a typing error. Instead of
producing an error message, the interpreter initializes the typing error as a new variable
with a value of 0. It can be very difficult to locate errors of this kind in your code.
Explicit Variable Declaration
To prevent errors caused by an implicit declaration of variables, OpenOffice.org Basic
provides a switch called:
Option Explicit
This must be listed in the first program line of each module and ensures that an error
message is issued if one of the variables used is not declared. The Option Explicit switch
should be included in all Basic modules.
In its simplest form, the command for an explicit declaration of a variable is as follows:
Dim MyVar
This example declares a variable with the name MyVar and the type variant. A variant is a
universal variable that can record all conceivable values, including strings, whole numbers,
floating point figures, and Boolean values. Here are a few examples of Variant variables:
MyVar = "Hello World" ' Assignment of a string
MyVar = 1 ' Assignment of a whole number
MyVar = 1.0 ' Assignment of a floating point number
MyVar = True ' Assignment of a Boolean value
The variables declared in the previous example can even be used for different variable
types in the same program. Although this provides considerable flexibility, it is best to
restrict a variable to one variable type. When OpenOffice.org Basic encounters an