UNDEF

UNDEF represents a particular state of parameters. The value of a parameter in this state cannot be accessed, it is undefined.

At initialization (loading a compound) all parameters receive the state UNDEF, provided they do not have an initialization value assigned in the parameter table.

A parameter or parameter group can also be assigned the UNDEF state (f$Undef or f$PGUndef).

If a parameter that is in the state UNDEF is queried in a condition or is used in an action (after the equal sign), it will automatically be inquired via a system dialog box.

Likewise, a special logic can be defined which is called in case of the value inquiry. This is done using the function f$UndefDT.

The only parameter query that does not trigger an automatic value inquiry is the check function f$IsUndef.

If a parameter is to specifically have no value and is not to be automatically inquired, it can be assigned the NOVAL state.