Constants

BASIC Guide

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• The Language of OpenOffice.org Basic

• Overview of a Basic Program
• Working With Variables
• Strings
• Numbers
• Boolean Values
• Date and Time
• Arrays
• Scope and Life Span of Variables
• Constants
• Operators
• Branching
• Loops
• Procedures and Functions
• Error Handling
• Other Instructions

• Runtime Library

• Conversion Functions
• Strings
• Date and Time
• Files and Directories
• Message and Input Boxes
• Other Functions

• Introduction to the API

• Universal Network Objects (UNO)
• Properties and Methods
• Modules, Services and Interfaces
• Tools for Working with UNO
• Overview of Central Interfaces

• Working with Documents

• The StarDesktop
• Styles and Templates

• Text Documents

• The Structure of Text Documents
• Editing Text Documents
• More than Just Text

• Spreadsheet Documents

• The Structure of Spreadsheets
  • Rows and Columns
  • Cells and Ranges
  • Formatting Spreadsheet Documents
• Editing Spreadsheet Documents

• Drawings and Presentations

• The Structure of Drawings
• Editing Drawing Objects
• Presentations

• Charts (Diagrams)

• Using Charts in Spreadsheets
• The Structure of Charts
• Chart Types

• Databases

• SQL: a Query Language
• Types of Database Access
• Data Sources
• Database Access

• Dialogs

• Working With Dialogs
• Properties
• Events
• Dialog Control Elements

• Forms

• Working With Forms
• Control Element Forms
• Database Forms

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Constants are values which may be used but not changed by the program.

Defining Constants

In OpenOffice.org Basic, use the keyword Const to declare a constant.

Const A = 10
Const B = A+5
Const Hi = "Hello World"

Do not specify the constant type in the declaration : it will be silently ignored. This code shows that you do not get the type that you specify. Const alpha As Long = 1 Const beta As Single = 3.1 Const gamma As Boolean = True Const delta As Currency = 123456.05 Const phi As Long = 32768 MsgBox(TypeName(alpha)) ' displays : Integer MsgBox(TypeName(beta)) ' displays : Double MsgBox(TypeName(gamma)) ' displays : Integer MsgBox(TypeName(delta)) ' displays : Double MsgBox(TypeName(phi)) ' displays : Double As Basic makes automatic type conversions, there is usually no problems using a constant in an expression. If you want to specify the type of a data, use a typed variable, not a constant.

Scope of Constants

Constants have the same scope as variables (see Scope and Life Span of Variables), but the syntax is slightly different. A Const definition in the module header is available to the code in that module. To make the definition available to other modules, add the Public keyword.

Public Const one = 1

Predefined Constants

OpenOffice.org Basic predefines several constants. Among the most useful are:

• True and False, for Boolean assignment statements
• PI as a type Double numeric value

Dim bHit as Boolean
bHit = True

Dim dArea as Double, dRadius as Double
' ... (assign a value to dRadius)
dArea = PI * dRadius * dRadius

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