Scratch that! (I shouldn't be up so late at night...)
My previous version of maxint wasn't returning a reliable integer, but sometimes floating point. Revised experiment: JVERSION Engine: j701/2011-01-10/11:25 build: Feb 6 2011 16:16:29 Library: 7.01.043 Platform: Darwin 64 Installer: j701a_mac64.dmg InstallPath: /Applications/j64-701 maxint 3 : 0 z=. <. 2^(y-1) <. z+(z-1) ) (aa-1)=aa=: maxint 44 0 (aa-1)=aa=: maxint 45 0 (aa-1)=aa=: maxint 63 0 (aa-1)=aa=: maxint 64 1 _1 + 2^63x 9223372036854775807 maxint 63 9223372036854775807 datatype maxint 63 integer datatype _1+maxint 63 integer datatype 1+maxint 63 floating ...the tipping-point. which is no surprise at all with 64 bit integers. Verb: factors -still can't factorize (maxint 63). But if I integerize the intermediates, it doesn't hang, now. And it can actually factorize (maxint 60): (a=z);(a=: */ff);z;(ff=: factors z=: maxint 60) ┌─┬───────────────────┬───────────────────┬─────────────────────────────────────┐ │1│1152921504606846975│1152921504606846975│3 3 5 5 7 11 13 31 41 61 151 331 1321│ └─┴───────────────────┴───────────────────┴─────────────────────────────────────┘ But it gets it wrong sporadically starting with maxint 53 ... (a=z);(a=: */ff);z;ff=: factors z=: maxint 53 ┌─┬────────────────┬────────────────┬────────────────┐ │0│9007199254740992│9007199254740991│9007199254740992│ └─┴────────────────┴────────────────┴────────────────┘ What seems to be happening is that the computation of intermediate y overflows, and becomes imprecise. Haven't isolated what's causing j64 to hang. But I suspect Line 5 of: factors, when it gets a floating y. > JVERSION > Engine: j701/2011-01-10/11:25 build: Feb 6 2011 16:16:29 > Library: 7.01.043 > Platform: Darwin 64 > Installer: j701a_mac64.dmg > > InstallPath: /Applications/j64-701 > (z-1) = z=: maxint 44 > 0 > (z-1) = z=: maxint 45 > 1 > > ...no different. > (Why should I be surprised at that?) ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
