A few handy tests which are good to know: N=: GI *. 1 0 e.~ * NB. naturals Z=: GI *. R NB. integers R=: = + NB. reals C_R=: + = - NB. pure imaginaries (C-.R) GI=: = <. NB. gaussian integers
These were made to accept any J number. They could be optimised if one knows that they are working only with real numbers, for example. In that case 1 0 e.~ * could be replaced by >:&0 and the test for reals can be skipped in Z. In addition, these work with the mathematical definitions of the different number sets, not with J's internal storage types. Louis > On 9 Aug 2017, at 11:42, Skip Cave <s...@caveconsulting.com> wrote: > > Martin, > > The original problem I was working on was a post on Quora ( > https://goo.gl/NrZde2). I use these Quora math questions to help sharpen my > J skills. I try to see if I can "brute force" the solutions using J, while > most other posters try to solve these things by algebraic manipulation. My > answer to that question is here: (https://goo.gl/FhdJAg). There are several > Quora problems that I have posted J solutions for, mostly to show how > simple a brute force solution can be when using an array language. You can > find those posts by searching for my name ("Skip Cave") in Quora > > In this problem all I really needed to do was to find all the results from > the equation that were integers, so I used the 0=1|| scheme to find them. > > Our discussion on the J forum got me thinking about finding both the > fractional part and the integer part of numbers, and I thought the pair of > verbs (fp, ip) would be a nice addition to the Phrases doc, which is > defined as listing phrases "useful to beginners in learning the language, > and of continuing use to practical programmers." > > Also, when I obtained the fractional part, I wanted to keep the fact that > the fractional part came from a negative number, hence the attempt to have > negative fractional parts. > > Skip > > Skip Cave > Cave Consulting LLC > >> On Wed, Aug 9, 2017 at 9:35 AM, Martin Kreuzer <i...@airkreuzer.com> wrote: >> >> From what I've gathered so far is, that people seem to not mind that much, >> when extracting the fractional part from a (negative) float, they use >> >> (1&|) _8.11 >> 0.89 >> >> or >> >> (1&#:) _8.11 >> 0.89 >> >> or >> >> (**1||) _8.11 >> _0.11 >> >> as long as the integer and fractional part added up produce the original >> float value. >> >> Q: Would somebody care to give a (scaled down) real-world example so as to >> give me a chance to understand where this ip/fp extraction usually comes >> into play and what part of the data is used for decision-making..? Thanks. >> >> -M >> >> >> > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
