Hi Ed, I was thinking of explaining Roger's sqrt code as part of next month's NYCJUG. You should take a look: https://www.meetup.com/J-Dynamic-Functional-Programming/ . Cheers, Devon
On Fri, Apr 22, 2022 at 12:49 AM Ed Gottsman <edward.j.gotts...@gmail.com> wrote: > Thanks to everyone who responded and in particular for the link to Roger > Hui’s essay. The wiki discussion was also very good. > > (In an earlier life I disparaged “cargo cult” programming, in which you > take a few lines of source you don’t understand and integrate them into > your program. [That you effectively do the same thing when you adopt > someone else’s compiled library cut no ice with me.] J has forced me to > relax a bit in that regard and I will probably adopt some of Roger’s code > without entirely understanding it. :-) ) > > Thanks again. > > Ed > > Sent from my iPad > > > On Apr 21, 2022, at 8:18 PM, Gilles Kirouac <g1...@myriade.ca> wrote: > > > > Ed If you expand the Extended Integers section (below by bob), you will > see a link to an essay by Roger on 'Extended Precision Functions'. There is > a Square Root verb. > > > > NB. long rational result may exceed line length > > sqrt 1x + *: 999999999x > > > 1249999998750000000625000000625000000468750000156249999765624999453r1250000000000000000000000000000000000000000000000000000000 > > sqrt *: 999999999x > > 999999999 > > > > > > ~ Gilles > > > >> Le 2022-04-21 à 14:50, 'robert therriault' via Programming a écrit : > >> Gilles, > >> In Nuvoc the extended constant notation can be found here > https://code.jsoftware.com/wiki/Vocabulary/Constants#Extended_Integers > >> Having said that, it is hidden pretty well and most of its references > are previous documentation on the jsoftware site. There is certainly work > to be done on the wiki! > >> Cheers, bob > >>>> On Apr 21, 2022, at 11:44, Gilles Kirouac <g1...@myriade.ca> wrote: > >>> > >>> Ed > >>> > >>> You seem unaware of the extended precision constant notation: > >>> > >>> "digits with a trailing x denote an extended precision integer" > >>> > >>> https://www.jsoftware.com/help/dictionary/dcons.htm > >>> [Where is the equivalent in NuVoc?] > >>> > >>> I would rather write > >>> > >>> 1x + *: 999999999x > >>> 999999998000000002 > >>> > >>> ~ Gilles > >>> > >>> Le 2022-04-21 à 12:51, Henry Rich a écrit : > >>>> 3!:0 %: x: 1 + x: *: x: 999999999 > >>>> 8 > >>>> The square root cannot be represented exactly. > >>>> Henry Rich > >>>> On 4/21/2022 12:43 PM, Ed Gottsman wrote: > >>>>> Hello. > >>>>> I’m working on the Project Euler “Diophantine equation” problem > (#66) and using J’s extended precision facilities. I’ve run into behavior > that confuses me. Boiled down (and overusing x: just to be sure): > >>>>> x: %: x: 1 + x: *: x: 999999999 > >>>>> 999999999 > >>>>> That is (if my syntax is right), the square root of (one plus the > square of a really large n) is n. I’m apparently misunderstanding > something about extended precision. I’ve tried it with a variety of uses > of x: but to no avail, and as I read the x: documentation…this is an odd > result. > >>>>> > >>>>> Any help would be much appreciated. > >>>>> (J901 on iPadOS, for which sincere kudos to Ian Clark.) > >>>>> Many thanks. > >>>>> Ed > >>>>> > ---------------------------------------------------------------------- > >>>>> 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 > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > -- Devon McCormick, CFA Quantitative Consultant ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
