Difference between revisions of "Documentation/BASIC Guide/Constants"

Revision as of 07:16, 12 July 2018

>]]

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

Defining Constants

In Apache OpenOffice 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