---Graham Parkhouse wrote: > sum=: 10 12 14 15 15 17 18 19 20 22 17 19 20 21 22 24 24 25 27 29 > > Next I would like to get a list of the indices of sum whose > values only > appear once, i.e. > > 0 1 2 6 13 17 18 19
> Why doesn't this give it to me? > > sum ((1&[EMAIL PROTECTED])#])/. i.#sum >From the dictionary page for key: u/. u is applied to each collection of y having identical keys. In your case u is a fork (1&[EMAIL PROTECTED] # ]) i.e. (f g h). You don't want to apply the fork to each collection of y, you want apply copy (#) to the result of f/. and h/. except that you want h to be < rather than ] (to see why try: sum ]/. i.#sum). This works: ((1&=@:#/. ;@:# </.) [EMAIL PROTECTED]) sum 0 1 2 6 13 17 18 19 > Is there an altogether different way to get the result I want? Probably, but I'll leave that for others! ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
