defined() returns true if a label or macro is defined, false otherwise; undefined() returns true if the label or macro is undefined.
Syntax
defined(label)
undefined(label)
Remarks
Constant values are implicitly defined. Macro definitions are checked before label definitions.
Example
Automatically setting DebugLevel to 10 if previously undefined when Debug is defined.
#define Debug #if defined(Debug) && undefined(DebugLevel) DebugLevel = 10 .echoln "Debug level set to 10." #endif