Perhaps i.~ is a viable line of attack. It's quite fast. Here are a few
variations on a theme:
({ ((_1 + #@:[ +/\@:~: (i.i.)) 1 + >./) ) i.~ y NB. A
({ (* _1++/\)@:(~:)@:({.~ 1 + >./) ) i.~ y NB. B
({i.@:#@:]`]`(#&0@:(1+>./@:]))}~@:~.@:({.~1+>./)) i.~y NB. C
For the subdomain where the nub of y is clustered at the front, these are
faster than (~.y) i. y . But for y as given (where >./i.~y is normally
large), the nub method is faster.
0.000128787 NB. (~.y) i. y
0.000369041 NB. A
0.00032546 NB. B
0.000344737 NB. C
-Dan
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
