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Conditionally includes a set of commands at compile time if a compile-time constant is defined.
#IFDEF | #IFNDEF ConstantName
Commands
[#ELSE
Commands]
#ENDIF |
Parameters
- #IFDEF
-
Specifies that a set of commands is included at compile time when the ConstantName is defined.
The following items describe how a set of commands is included at compile time when you include #IFDEF:
-
If ConstantName is defined, the set of commands following #IFDEF and preceding #ELSE or #ENDIF (whichever occurs first) is included at compile time.
-
If ConstantName is not defined and #ELSE is included, the set of commands following #ELSE and preceding #ENDIF is included at compile time.
-
If ConstantName is not defined and #ELSE is not included, no commands within the #IFDEF ... #ENDIF structure are included at compile time.
-
If ConstantName is defined, the set of commands following #IFDEF and preceding #ELSE or #ENDIF (whichever occurs first) is included at compile time.
- #IFNDEF
-
Specifies that a set of commands is included at compile time when the ConstantName is not defined.
The following items describe how a set of commands is included at compile time when you include #IFNDEF:
-
If ConstantName is not defined, the set of commands following #IFNDEF and preceding #ELSE or #ENDIF (whichever occurs first) is included at compile time.
-
If ConstantName is defined and #ELSE is included, the set of commands following #ELSE and preceding #ENDIF is included at compile time.
-
If ConstantName is defined and #ELSE is not included, no commands within the #IFNDEF ... #ENDIF structure are included at compile time.
-
If ConstantName is not defined, the set of commands following #IFNDEF and preceding #ELSE or #ENDIF (whichever occurs first) is included at compile time.
- ConstantName
- Specifies the compile-time constant whose existence determines whether a set of commands is included at compile time. Compile-time constants are defined with #DEFINE.
- Commands
- Specifies the set of commands that is included at compile time.
Remarks
You can nest an #IFDEF | #IFNDEFВ ...В #ENDIF structure within another #IFDEF | #IFNDEFВ ...В #ENDIF structure.
Comments can be placed on the same line after #IFDEF, #IFNDEF, #ELSE, and #ENDIF. These comments are ignored during compilation and program execution.
Example
The following example creates a compile-time constant named MYDEFINE. #IFDEF ...В #ENDIF displays a message if the compile-time constant has been defined.
| В |  Copy Code |
|---|---|
#DEFINE MYDEFINE 1 #IFDEF MYDEFINE WAIT WINDOW "MYDEFINE exists" #ELSE WAIT WINDOW "MYDEFINE does not exist" #ENDIF | |