Hello, yes the number is very big, but why if I don't use the extended precision I have "infinity" as result, and if I use it I got an error ?
I should get infinity anyways. this is my J session: ^/ 2 2 2 2 65536 ^/ 2 2 2 2 2 NB. do not use extended precision and I have "+inf" _ ^/ 2 2 2 2 2 2 NB. do not use extended precision and I have "+inf" _ ^/ x: 2 2 2 2 2 NB. using extended precision I have the result (part of it) 2003529930406846464979072351560255750447825475569751419265016973710894059556311453089506130880933348101038234342907263181822949382118812668869506364761547029165041871916351587966347219442930927982084309104855990570159318959639524863372367203002916969592156... ^/ x: 2 2 2 2 2 2 NB. using extended precision I have error... not "+inf" |limit error | ^/x:2 2 2 2 2 2 https://en.wikipedia.org/wiki/Knuth%27s_up-arrow_notation thanks, Fausto 2015-02-17 18:55 GMT+01:00 'Pascal Jasmin' via Programming <[email protected]>: > 2 ^. ^/ 5 # 2x > 65536 > > so at just 5, it is a 65k bit number > > at 6, the 2log of that number would be that 65kbit number. The number of > atoms in the universe is an 80 bit number. > > > > > > ----- Original Message ----- > From: Raul Miller <[email protected]> > To: Programming forum <[email protected]> > Cc: > Sent: Tuesday, February 17, 2015 12:32 PM > Subject: Re: [Jprogramming] Fwd: Hello all! > > I would guess that the number you are generating is too big to be > represented using J's data structures (which would also suggest that > it would be too big to fit into memory). > > Thanks, > > -- > Raul > > On Tue, Feb 17, 2015 at 12:12 PM, Fausto Saporito > <[email protected]> wrote: >> HI! >> >> I'm a new J user with a little experience of APL and LISP. >> >> In these days I'm playing with big numbers... very big indeed, and I >> found a bug (?) in the exteded precision implementation of J. >> >> I'm not sure if I can call it a bug, but if I use the standard >> precision number I got a "infinity" as result... as should be. >> >> I'm talking about knuth-up-arrow notation, to build the "tower of >> power". In J the syntax is amazingly simple : ^/ 2 2 2 2 >> >> 2^^4 is 2 * (2* (2* 2)) = 65536 >> >> Now 2^^5 is _ with standard precision... but if I use x: (i.e. ^/ x: >> 2 2 2 2 2) can get most of number... it's quite big indeed. >> >> The problem arises with 2^^6 or 3^^4 I get "limit error" instead of _ ... >> why ? >> >> Is it an expected behaviour ? >> >> thanks in advance, >> Fausto >> ---------------------------------------------------------------------- >> 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
