" It is very difficult to express Mathematics on an ASCII page"
One way is to use the Unicode number for the symbol. Also/or use names with parentheses for the symbol. It is then easy to replace the corresponding J operation 2009/4/23 Don Watson <[email protected]> > Thanks, Bill, > > Under no circumstances do I want to bother experienced and effective J > users like yourself with change. I did say originally that: "The existence > of a J mutation would need to be totally transparent to J programmers, > requiring them to make no adjustments whatsoever." I only want to attract a > much larger group of potential users - teachers - a group that intersects > little with J users. > > The only reason that I submitted this to the chat forum was to get some > help. It has been successful. I have had a lot of help and am very grateful > for it. > > It is very difficult to express Mathematics on an ASCII page, but I will > do my best. I will use Ric's method of representing Sigma with a large "E" > and "/" for square root. In a classroom, I would want to develop the > mathematical formula - maybe on a blackboard or Powerpoint - in parallel > with an S model. As the formula develops, it can be tested at each step > with > the S model (which would be the same as the J model until we try to store > it). In what is below, the mathematical formula is after NB. > > In doing this, you will note that there is nothing that that resembles > Computer Science. No subroutines, one line only and no administrative > inserts like: program =: dyad : 0. S - or unstored explicit one line J > - > is just an alternative language for expressing mathematical formulae. > > One might ask whether two languages at the same time can cause > confusion. I can only say that some of my grandchildren have gone > through French immersion programs where they learn in French. > Their English is better as a result, because the differences highlight > the structure of language and it has helped them better understand > their own language. > > Don. > > ========== J session =========================================== > NB. The sum of the values is: > +/y NB. Ey > 24 > NB. the number of values is: > #y NB. N > 6 > NB. the sum divided by the number is: > 24 % 6 > 4 > NB. We can do this in one step: > (+/y) % #y NB. Ey/N > 4 > NB. The deviations from the mean are: > y - (+/y) % #y NB. y - Ey/N > 0 1 2 _2 _1 0 > NB. the sum of their squares is > +/ *: 0 1 2 _2 _1 0 > 10 > NB. or combined: > 2 > +/ *: y - (+/y) % #y NB. E (y - Ey/N) > 10 > NB. now multiply by the reciprocal of > 1 less than the number of values 2 > (%<:#y) * +/ *: y - (+/y) % #y NB. 1/N-1 E (y - Ey/N) > > NB. and finally take the square root: > %: (%<:#y) * +/ *: y - (+/y) % #y 2 > ~ NB. / 1/N-1 E (y - Ey/N) > 1.41421 > NB. It is again helpful to define the formula as a verb for easy reuse. > stddev=: %: (%<:#y) * +/ *: (]) - (+/) % # 2 > NB. stddev = / 1/N-1 E (y - Ey/N) > stddev y > 1.41421 > stddev 3 7 4 5 8 2 3 4 5 > 1.94365 > ===================================================== > > ---- Original Message ----- > From: "bill lam" <[email protected]> > To: <[email protected]> > Sent: Thursday, April 23, 2009 10:16 AM > Subject: Re: [Jchat] Language S > > > > On Thu, 23 Apr 2009, Don Watson wrote: > >> %: (<:#y) %~ +/ *: y - (+/y) % #y > >> 1.41421 > >> NB. It is again helpful to define the formula as a verb for easy > >> reuse. > >> NB. Remember from all our previous work that before we store it, > >> we take out all of the "y"s to the left of a right parenthesis > >> NB. Where a "y" is to the left of a verb, we need to replace it with > >> (]) > >> stddev=: %: (<:#) %~ +/ *: (]) - (+/) % # > > > > I see you point now. It is easier to arrive a pseudo tacit form > > without knowing what a fork is. However I prefer to write tacit form > > if that is within my capacity otherwise I just write explicit > > definition shamelessly, not even bother to cheat with `13 :'. > > > > -- > > regards, > > ==================================================== > > GPG key 1024D/4434BAB3 2008-08-24 > > gpg --keyserver subkeys.pgp.net --recv-keys 4434BAB3 > > 唐詩028 韋應物 初發揚子寄元大校書 > > 悽悽去親愛 泛泛入煙霧 歸棹洛陽人 殘鐘廣陵樹 > > 今朝為此別 何處還相遇 世事波上舟 沿洄安得住 > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > -- Björn Helgason, Verkfræðingur Fugl&Fiskur ehf, Þerneyjarsundi 23, Hraunborgum Po Box 127,801 Selfoss , t-póst: [email protected] gsm: +3546985532 Landslags og skrúðgarðagerð, gröfuþjónusta http://groups.google.com/group/J-Programming Tæknikunnátta höndlar hið flókna, sköpunargáfa er meistari einfaldleikans góður kennari getur stigið á tær án þess að glansinn fari af skónum /|_ .-----------------------------------. ,' .\ / | Með léttri lund verður | ,--' _,' | Dagurinn í dag | / / | Enn betri en gærdagurinn | ( -. | `-----------------------------------' | ) | (\_ _/) (`-. '--.) (='.'=) ♖♘♗♕♔♙ `. )----' (")_(") ☃☠ ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
