Difference between revisions of "Documentation/BASIC Guide/Constants"
(→Scope of Constants: + Predefined Constants section) |
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<source lang="oobas"> | <source lang="oobas"> | ||
Const A = 10 | Const A = 10 | ||
| + | Const B = A+5 | ||
| + | Const Hi = "Hello World" | ||
</source> | </source> | ||
| − | + | {{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. | ||
| + | <source 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 | ||
| + | </source> | ||
| + | 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. | ||
| + | }} | ||
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| − | |||
| − | |||
== Scope of Constants == | == Scope of Constants == | ||
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<source lang="oobas"> | <source lang="oobas"> | ||
| − | Public Const one | + | Public Const one = 1 |
</source> | </source> | ||
== Predefined Constants == | == Predefined 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"
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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
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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