Using Procedures and Functions

The following describes the basic use of procedures and functions in LibreOffice Basic.

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When you create a new module, LibreOffice Basic automatically inserts a SUB called "Main". This default name has nothing to do with the order or the starting point of a LibreOffice Basic project. You can also safely rename this SUB.

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Some restrictions apply for the names of your public variables, subs, and functions. You must not use the same name as one of the modules of the same library.

Procedures (SUBS) and functions (FUNCTIONS) help you maintaining a structured overview by separating a program into logical pieces.

One benefit of procedures and functions is that, once you have developed a program code containing task components, you can use this code in another project.

Passing Variables to Procedures (SUB) and Functions (FUNCTION)

Variables can be passed to both procedures and functions. The SUB or FUNCTION must be declared to expect parameters:

Sub SubName(Parameter1 As Type, Parameter2 As Type,...)
Program code
End Sub

The SUB is called using the following syntax:

SubName(Value1, Value2,...)

The parameters passed to a SUB must fit to those specified in the SUB declaration.

The same process applies to FUNCTIONS. In addition, functions always return a function result. The result of a function is defined by assigning the return value to the function name:

Function FunctionName(Parameter1 As Type, Parameter2 As Type,...) As Type
Program code
End Function

The FUNCTION is called using the following syntax:

Variable=FunctionName(Parameter1, Parameter2,...)
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You can also use the fully qualified name to call a procedure or function:
For example, to call the Autotext macro from the Gimmicks library, use the following command:

Passing Variables by Value or Reference

Parameters can be passed to a SUB or a FUNCTION either by reference or by value. Unless otherwise specified, a parameter is always passed by reference. That means that a SUB or a FUNCTION gets the parameter and can read and modify its value.

If you want to pass a parameter by value insert the key word "ByVal" in front of the parameter when you call a SUB or FUNCTION, for example:

Result = Function(ByVal Parameter)

In this case, the original content of the parameter will not be modified by the FUNCTION since it only gets the value and not the parameter itself.

Scope of Variables

A variable defined within a SUB or FUNCTION, only remains valid until the procedure is exited. This is known as a "local" variable. In many cases, you need a variable to be valid in all procedures, in every module of all libraries, or after a SUB or FUNCTION is exited.

Declaring Variables Outside a SUB or FUNCTION

Global VarName As TYPENAME

The variable is valid as long as the LibreOffice session lasts.

Public VarName As TYPENAME

The variable is valid in all modules.

Private VarName As TYPENAME

The variable is only valid in this module.


The variable is only valid in this module.

Example for private variables

Enforce private variables to be private across modules by setting CompatibilityMode(true).

' ***** Module1 *****
Private myText As String
Sub initMyText
    myText = "Hello"
    Print "In module1 : ", myText
End Sub
' ***** Module2 *****
'Option Explicit
Sub demoBug
    CompatibilityMode( true )
    ' Now returns empty string
    ' (or raises error for Option Explicit)
    Print "Now in module2 : ", myText
End Sub

Saving Variable Content after Exiting a SUB or FUNCTION

Static VarName As TYPENAME

The variable retains its value until the next time the FUNCTION or SUB is entered. The declaration must exist inside a SUB or a FUNCTION.

Specifying the Return Value Type of a FUNCTION

As with variables, include a type-declaration character after the function name, or the type indicated by "As" and the corresponding key word at the end of the parameter list to define the type of the function's return value, for example:

Function WordCount(WordText As String) As Integer

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