Difference between revisions of "Documentation/BASIC Guide/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. |
<source lang="oobas"> | <source lang="oobas"> | ||
| Line 49: | Line 49: | ||
== Predefined Constants == | == Predefined Constants == | ||
| − | {{ | + | {{AOo}} Basic predefines several constants. Among the most useful are: |
*<tt>True</tt> and <tt>False</tt>, for Boolean assignment statements | *<tt>True</tt> and <tt>False</tt>, for Boolean assignment statements | ||
*<tt>PI</tt> as a type <tt>Double</tt> numeric value | *<tt>PI</tt> as a type <tt>Double</tt> numeric value | ||
Revision as of 13:32, 27 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"
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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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