x=: 10 20 30 in the examples. On Thu, Jan 14, 2016 at 10:57 PM, Roger Hui <[email protected]> wrote:
> Empty frame, or more accurately zero frames, if it is said to be for > anything, is to allow edge cases, the case where the frame contains a 0, to > work without a lot of exceptions, without the programmer having to write > extra code. An example hopefully illustrates this point. > > x ,"1 y=: i.3 4 > 10 20 30 0 1 2 3 > 10 20 30 4 5 6 7 > 10 20 30 8 9 10 11 > > In this case the left frame is '' and the right frame is }:$y, (,3) in > this case. > > x ,"1 y=: i.2 4 > 10 20 30 0 1 2 3 > 10 20 30 4 5 6 7 > x ,"1 y=: i.1 4 > 10 20 30 0 1 2 3 > x ,"1 y=: i.0 4 > > The right frames in the successive examples are (,2), (,1), and (,0). The > last is an example of a zero frame, and the example worked with no fuss. > The following sequence makes more salient the consistent treatment of > frames, including zero frames. > > $ x,"1 y=: i.3 4 > 3 7 > $ x,"1 y=: i.2 4 > 2 7 > $ x,"1 y=: i.1 4 > 1 7 > $ x,"1 y=: i.0 4 > 0 7 > > The reason why zero frames requires extra discussion is because ordinarily > you have argument cell(s) for the verb to apply to, and the result cells > and hence the result is not in question. With zero frames, there are no > argument cells, so the system needs to do something extra (so that you > don't have to). (x,"1 y appends vectors to vectors, but when y is i.0 4 it > does not have any vectors.) > > > > On Thu, Jan 14, 2016 at 10:35 PM, Matthew Baulch <[email protected]> > wrote: > >> And the dictionary defines frame.... such that it may be empty? I'm most >> interested in whether, supposing this is the case, allowing empty frames >> serve (an)other purpose(s) in the structure of the language. >> >> Apologies if my original phrasing was unclear. >> >> Every decision in the design of J seems very deliberate—which I really >> appreciate. It just seems that empty frames must serve a purpose. Trying >> to >> work it out. >> On 15 Jan 2016 4:21 pm, "bill lam" <[email protected]> wrote: >> >> > The J dictionary is always correct. >> > >> > Пт, 15 янв 2016, Matthew Baulch написал(а): >> > > Fair enough, though I can't work out whether the dictionary agrees >> with >> > > NuVoc here or not. Either way, which definition of frame is correct? >> > > On 15 Jan 2016 3:48 pm, "bill lam" <[email protected]> wrote: >> > > >> > > > For J implemention, the only authority is the J dictionary since >> > > > it defines the J language. You need not worry anything else. >> > > > >> > > > http://www.jsoftware.com/help/dictionary/dictb.htm >> > > > >> > > > Пт, 15 янв 2016, Matthew Baulch написал(а): >> > > > > I assume the intended definition of 'frame', in relation to verb >> > > > arguments, >> > > > > is that given on >> > > > > >> > > > > http://code.jsoftware.com/wiki/Vocabulary/FramingFill >> > > > > >> > > > > I'm just trying to understand verb/argument combinations with >> empty >> > > > > frame--the most common case, I suppose. >> > > > > >> > > > > From the wording "each argument is ... an array of [r-cells]. The >> > frame >> > > > ... >> > > > > is the shape of this array of [r-cells]", it seems that a frame >> > should >> > > > > never be empty, but in fact have a minimum shape of '1'. Of >> course, >> > this >> > > > > ties into the wording of many other statements. In the case of >> dyadic >> > > > > verbs, for instance, >> > > > > >> > > > > "frames must agree ... they must be identical or one must be a >> > prefix of >> > > > > the other" (stated in link above) >> > > > > >> > > > > as opposed to >> > > > > >> > > > > "frames must agree ... one must have shape 1 or be a prefix of the >> > other" >> > > > > (the way I see it, assuming equality implies prefix-of) >> > > > > >> > > > > Can anyone shed some light on this? Is there an important reason >> for >> > this >> > > > > convention that I'm missing, or is it of little consequence? >> > > > > >> > > > > I'm implementing (or trying to...) a subset of J for the JVM, and >> > this is >> > > > > one little detail that's bothering me. >> > > > > >> > > > > Thanks. >> > > > > >> > > > > Matt Baulch >> > > > > >> > ---------------------------------------------------------------------- >> > > > > For information about J forums see >> > http://www.jsoftware.com/forums.htm >> > > > >> > > > -- >> > > > regards, >> > > > ==================================================== >> > > > GPG key 1024D/4434BAB3 2008-08-24 >> > > > gpg --keyserver subkeys.pgp.net --recv-keys 4434BAB3 >> > > > gpg --keyserver subkeys.pgp.net --armor --export 4434BAB3 >> > > > >> ---------------------------------------------------------------------- >> > > > For information about J forums see >> http://www.jsoftware.com/forums.htm >> > > ---------------------------------------------------------------------- >> > > For information about J forums see >> http://www.jsoftware.com/forums.htm >> > >> > -- >> > regards, >> > ==================================================== >> > GPG key 1024D/4434BAB3 2008-08-24 >> > gpg --keyserver subkeys.pgp.net --recv-keys 4434BAB3 >> > gpg --keyserver subkeys.pgp.net --armor --export 4434BAB3 >> > ---------------------------------------------------------------------- >> > For information about J forums see http://www.jsoftware.com/forums.htm >> ---------------------------------------------------------------------- >> For information about J forums see http://www.jsoftware.com/forums.htm > > > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
