Difference between revisions of "Documentation/BASIC Guide/Constants"
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| + | {{DISPLAYTITLE:Constants}} | ||
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Constants are values which may be used but not changed by the program. | Constants are values which may be used but not changed by the program. | ||
== Defining Constants == | == Defining Constants == | ||
| − | In {{ | + | In {{AOo}} Basic, use the keyword <tt>Const</tt> to declare a constant. |
| + | |||
| + | <syntaxhighlight lang="oobas"> | ||
| + | Const A = 10 | ||
| + | Const B = A+5 | ||
| + | Const Hi = "Hello World" | ||
| + | </syntaxhighlight> | ||
| + | |||
| + | {{Warn|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. | |
| + | <syntaxhighlight lang="oobas"> | ||
| + | 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 | ||
| + | </syntaxhighlight> | ||
| + | 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 == | == Scope of Constants == | ||
| + | |||
Constants have the same scope as variables (see [[Documentation/BASIC Guide/Scope of Variables|Scope and Life Span of Variables]]), but the syntax is slightly different. A <tt>Const</tt> definition in the module header is available to the code in that module. To make the definition available to other modules, add the <tt>Public</tt> keyword. | Constants have the same scope as variables (see [[Documentation/BASIC Guide/Scope of Variables|Scope and Life Span of Variables]]), but the syntax is slightly different. A <tt>Const</tt> definition in the module header is available to the code in that module. To make the definition available to other modules, add the <tt>Public</tt> keyword. | ||
| − | + | <syntaxhighlight lang="oobas"> | |
| + | Public Const one = 1 | ||
| + | </syntaxhighlight> | ||
| + | == Predefined Constants == | ||
| + | |||
| + | {{AOo}} Basic predefines several constants. Among the most useful are: | ||
| + | *<tt>True</tt> and <tt>False</tt>, for Boolean assignment statements | ||
| + | *<tt>PI</tt> as a type <tt>Double</tt> numeric value | ||
| + | |||
| + | <syntaxhighlight lang="oobas"> | ||
| + | Dim bHit as Boolean | ||
| + | bHit = True | ||
| + | Dim dArea as Double, dRadius as Double | ||
| + | ' ... (assign a value to dRadius) | ||
| + | dArea = PI * dRadius * dRadius | ||
| + | </syntaxhighlight> | ||
| + | |||
| + | {{InterWiki Languages BasicGuide|articletitle=Documentation/BASIC Guide/Constants}} | ||
{{PDL1}} | {{PDL1}} | ||
Latest revision as of 11:09, 30 January 2021
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
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
| Content on this page is licensed under the Public Documentation License (PDL). |
