[GRASSLIST:6629] v.net.iso: some roads cost, others distance: sorry

[Dan Jacobson]

v.net.iso afcolumn=cost allows us to use a cost instead of a distance
for segments.

OK, what if on some of my roads I want to use cost, and some I want to
use distance?

Surprise surprise, nope. It's either all cost, all distance, or close
the road with -1.

Forget about DELETE FROM table WHERE cat =
road_I_want_measured_by_distance, v.net.iso will go nuts.

OK, then what are you going to set its value to in the table, -1? 0?
-1 is for closed roads. 0 is for 0 cost roads.

Nope. "The software engineers never considered this possibility."!!!

The solution for now would be: if the row is not found in the table,
then measure distance. Better would be -2: use distance.