On Thu, Mar 4, 2010 at 7:52 AM, Roger Hui <[email protected]> wrote:
> ,~/ involves lots of data movement whereas -~/ does not. > > The "special codes" are documented in > Appendix B of the dictionary. > http://www.jsoftware.com/help/dictionary/special.htm > > -~/ is not supported by special code. You can confirm > that by comparing the timings for +/ -/ and -~/ . > > You would avoid ,~/ for reasons other than machine > efficiency: ,|. (or just |. for vectors) are more direct, > i.e. more brain efficient. > > ah. Now I know why. ,~/ in J is more like '++'(append to a list, an O(n) for each element) in Haskell rather than the (:) which is an O(1) . I know |. serve the same purpose but tried to get a sense of what kind of function composition I should avoid. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
