Visual Basic and Visual FoxPro constants

VBA

Const

VFP

#DEFINE, #UNDEF, #INCLUDE

Visual Basic Syntax Notes

Constants in Visual Basic can be Private (the default) or Public and can optionally be defined as having a data type:

Public Const VAT_RATE As Single = 0.175

Visual Basic for Applications has a wide range of useful system constants such as vbBlue built into the language. Use the Object Browser from the View menu in the Visual Basic window to search for constants.

[VBA Object Browser]

Visual FoxPro Syntax Notes

Constants in Visual FoxPro are neither Public nor Private in the normal sense of the terms. They exist from the moment that they are created with #DEFINE until the moment that they are released with #UNDEF:

#DEFINE CTRL_C 3 * CTRL_C now exists in all * the lines of FoxPro code * which may be in several different modules * until it is undefined like this: #UNDEF CTRL_C

Do not try to put an '=' sign into the declaration of the constant.

Visual Foxpro include files

[Include constants in a Visual FoxPro class] FoxPro also has the #INCLUDE directive which pulls a header file of constants into the program. This makes maintenance easier because you can then keep all the constants for a project in one external file rather than having to cut and paste the #DEFINE statements into every module.

The FoxPro.H file supplied with the language includes the definitions of many useful constants such as COLOR_BLUE. Unlike Visual Basic, these are not built into the language itself.

A form or a class can also use a constant file. Rather than using the #INCLUDE statement you select Include File... from the Class or Form menu as appropriate. You can also set up the FoxPro options to specify a default include file.

It is possible to chain these include statements so that a project may have an include file which itself pulls in the standard FoxPro.H:

#INCLUDE FoxPro.H

*-- This indicates that there are no entries here - it starts with a "-" so that
*-- it sorts to the head of any list. Similarly for "All" entries.
#DEFINE NOENTRIES "-None-"
#DEFINE ALLENTRIES "-All- "


*-- We need something more meaningful than .F. and .T. when displaying
*-- Boolean values.
#DEFINE APP_FALSE "False"
#DEFINE APP_TRUE "True"

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