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
