OpenOffice.org BASIC Guide - OpenOffice.org wiki

Conversion Functions
The Val function is different from the Csng, Cdbl and Cstr methods. It converts a string into a number;
however it always expects a period to be used as the decimal point symbol.
Dim A As String
Dim B As Double
A = "2.22"
B = Val(A) ' Is converted correctly regardless of the
' country-specific settings
Checking the Content of Variables
In some instances, the date cannot be converted:
Dim A As String
Dim B As Date
A = "test"
B = A ' Creates error message
In the example shown, the assignment of the test string to a date variable makes no sense, so the Basic
interpreter reports an error. The same applies when attempting to assign a string to a Boolean variable:
Dim A As String
Dim B As Boolean
A = "test"
B = A ' Creates error message
Again, the basic interpreter reports an error.
These error messages can be avoided by checking the program before an assignment, in order to establish
whether the content of the variable to be assigned matches the type of the target variable. OpenOffice.org Basic
provides the following test functions for this purpose:
IsNumeric(Value)
checks whether a value is a number.
IsDate(Value)
checks whether a value is a date.
IsArray(Value)
checks whether a value is an array.
These functions are especially useful when querying user input. For example, you can check whether a user has
typed a valid number or date.
If IsNumeric(UserInput) Then
ValidInput = UserInput
Else
ValidInput = 0
MsgBox "Error message."
End If
In the previous example, if the UserInput variable contains a valid numerical value, then this is assigned to the
ValidInput variable. If UserInput does not contain a valid number, ValidInput is assigned the value 0 and
an error message is returned.
While test functions exist for checking numbers, date details and arrays in OpenOffice.org Basic, a corresponding
function for checking Boolean values does not exist. The functionality can, however, be imitated by using the
IsBoolean function:
Function IsBoolean(Value As Variant) As Boolean
On Error Goto ErrorIsBoolean:
Dim Dummy As Boolean
Dummy = Value
IsBoolean = True
On Error Goto 0
Exit Sub
ErrorIsBoolean:
Chapter 3 · Runtime Library 37