$ES[TACK] contains an integer count of the number of M virtual machine stack levels that have been activated and not removed since the last time $ESTACK was NEW'd.

A NEW $ESTACK saves the value of current $ESTACK and then sets its value to zero (0). If $ESTACK has not been NEW'd in the current execution path, $ESTACK=$STACK.


$ESTACK maybe used as a flag to indicate error traps invoked in particular stack levels needed to perform some different action(s). $ESTACK can be most useful in setting up a layered error trapping mechanism.

[Note] Note

GT.M does not permit $ESTACK to be SET, however $ESTACK can be NEWed.