Constants
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"
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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
Apache OpenOffice 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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