In addition 3!:1 and 3!:2 handle not just nouns, but defined verbs, adverbs and conjunctions.
On Tue, Apr 6, 2010 at 12:19 PM, Roger Hui <[email protected]> wrote: > I should add that 3!:1 and 3!:2 are efficient in time > and space, much more so than ": and ". . For example, > for integer arrays: > > x=: 1009 2003 ?...@$ 1e6 > ts=: 6!:2 , 7!:2...@] > ts '":x' > 0.389282 5.03404e7 > ts '3!:1 x' > 0.020751 8.38938e6 > */ $ ": x > 14146180 > $ 3!:1 x > 8084132 > > ts '".y' [ y=: ": x > 2.0132 8.78483e6 > ts '3!:2 y1' [ y1=: 3!:1 x > 0.0108416 8.38938e6 > > > > ----- Original Message ----- > From: Roger Hui <[email protected]> > Date: Tuesday, April 6, 2010 7:41 > Subject: Re: [Jprogramming] lines in display > To: Programming forum <[email protected]> > > > The binary representation > > http://www.jsoftware.com/help/dictionary/dx003.htm > > provides lossless representation of J arrays > > as a literal vector. e.g. > > > > y=: o. i.2 3 > > a=: 3!:1 y > > $a > > 72 > > type <'a' > > +----+ > > |noun| > > +----+ > > a 1!:2 <'\junk\xxx' > > y1=: 3!:2 (1!:1) <'\junk\xxx' > > y - y1 NB. i.e. bit-by-bit identical > > 0 0 0 > > 0 0 0 > > y -: y1 > > 1 > > y -:!.0 y1 NB. i.e. 0 tolerance, bit-by- > > bit identical > > 1 > > > > 3!:3 provides a related, more human-readable version of same. > > > > 2 (3!:3) y > > e200000000000000 > > 0000000000000008 > > 0000000000000006 > > 0000000000000002 > > 0000000000000002 > > 0000000000000003 > > 0000000000000000 > > 400921fb54442d18 > > 401921fb54442d18 > > 4022d97c7f3321d2 > > 402921fb54442d18 > > 402f6a7a2955385e > > > > There are also "components files" in the standard libraries. > > > > > > > > ----- Original Message ----- > > From: Ian Clark <[email protected]> > > Date: Tuesday, April 6, 2010 2:30 > > Subject: Re: [Jprogramming] lines in display > > To: Programming forum <[email protected]> > > > > > I was afraid that would be the answer. > > > > > > The inconvenience to my code is negligible. It just needs one more > > > line, with an (if.) in it. What distresses me is my failure to > > > understand why it happens. It makes me suspicious of my whole > > > data-storage approach. > > > > > > I need to store a 2-D integer array, call it z, in an ascii > > text file > > > and recover it on reloading the file. > > > Suppose 'a b'=:$z > > > Proviso: z is one of several arrays of mixed data. I want to > > > retain a > > > visual check on the file contents that they all match-up by rows > > > (numbered: i.a). Without this proviso, a sensible thing to do > > is to > > > store the contents of z as a vector and reconstruct it from a > > > knowledge of the number of rows, (a). > > > Taking a simple minded approach, however, I can use (":) to > > > stuff z in > > > a file, and (".) to recover it again from the (2-D) file > > image. This > > > seems adequate and reliable provided a>1 and b>1. I just > > > wouldn't have > > > anticipated it breaking down for b=1, which is not an uncommon > > > case to > > > arise. > > > > > > Clearly this is not the approach an experienced J-er would > > take, and > > > I'd like to know what that is. > > > > > > I don't want to drag this thread off-topic. It just seemed > > > related in > > > my mind to the problem of predicting the number of display- > > lines > > > in z > > > -- or do I mean (":z)? Or (". ":z)? > > > > > > Ian > > > > > > > > > On Tue, Apr 6, 2010 at 12:29 AM, Roger Hui > > <[email protected]> wrote: > > > > It's a feature, an inevitable consequence of numeric > > > > conversion and rank. If it breaks your code you have > > > > to rewrite your code. > > > > > > > > > > > > > > > > ----- Original Message ----- > > > > From: Ian Clark <[email protected]> > > > > Date: Monday, April 5, 2010 16:12 > > > > Subject: Re: [Jprogramming] lines in display > > > > To: Programming forum <[email protected]> > > > > > > > >> On not quite the same problem but a related one: > > > >> > > > >> If z is an integer table, under what conditions would you expect > > > >> ": z > > > >> to have the same number of rows as z? Under more restricted > > > >> conditions, when is (z -: ". ": z) ? > > > >> > > > >> Clearly you can't expect rank to be preserved if z=: i.1 3 - > > -since > > > >> under ": the information gets lost to enable you to > > > distinguish it > > > >> from i.3. But what about z=: i.3 1 ? > > > >> > > > >> Consider the following: > > > >> > > > >> (". ": i.z) ; i.z=: 3 2 > > > >> +---+---+ > > > >> |0 1|0 1| > > > >> |2 3|2 3| > > > >> |4 5|4 5| > > > >> +---+---+ > > > >> (". ": i.z) ; i.z=: 3 1 > > > >> +-----+-+ > > > >> |0 1 2|0| > > > >> | |1| > > > >> | |2| > > > >> +-----+-+ > > > >> > > > >> Is this a bug or a feature? (It's breaking my code, for > > which > > > I have > > > >> so far only found an inelegant fix). > > > >> > > > >> Ian > > > >> > > > >> > > > >> On Fri, Apr 2, 2010 at 10:20 PM, Roger Hui > > > <[email protected]> wrote: > > > >> > If x is a rank 2 or higher numeric array, how many > > > >> > lines are in the display of x? For example, > > > >> > there are 14 lines in the display of i. 3 4 5 . > > > >> > > > > >> > I've worked on a related problem on-and-off for years, > > > >> > starting in 1991, and only came to a good answer > > > >> > for this problem just a few days ago. > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
