Hi IMHO simpler and more flexible (works if there are lines not matching the pattern) is:
:let n=0 | g/opIndex(\zs\d\+/s//\=n/|let n+=1 A useful idiom I learned here. Usually I muck around with ordinary searches until the search highlighting shows I've got it right, then :let n=0|g//s//\=n/|let n+=1 is what I have to remember, and it's obvious what the start and increment are. John
