HP MLIB User's Guide Vol. 2 7th Ed.

624 HP MLIB User’s Guide
XERVEC VECLIB error handler
iarg If iarg > 0, the error message is printed in the first form
given above and iarg is the number of the argument
that was found to be in error. If iarg = 0, the error
message is printed in the second form shown and iarg
is not part of the error message. If iarg < 0, the error
message is printed in the third form shown and iarg is
the error number.
messag The text of the error message to be printed if iarg ≤ 0.
Not used as input if iarg > 0.