Board Thread:Program Announcements/@comment-25017421-20140603081447/@comment-5334617-20141126042027

Off the top of my head, a kludge might look something like:

IF TRIP(1,1)-TRIP(0,1)>0 THEN GOSUB@ISLOPE1CALC ELSE ISLOPE1=524287*SGN(TRIP(1,0)-TRIP(0,0))

This will set  to "nearly negative infinity" or "nearly positive infinity" as appropriate.