Thank you. I may reply more in a year ot two when I have fully grokked Roger’s note in your reply!
Wanting to be snippy in a complaint I was making to my local bank, I wanted to compare how many prime numbers my iPhone (using J) could calculate in the 15 seconds their cash machine took to read and recognize my cash card. Rodger's note may have held the answer to that; but I never found the answer I was seeking. > On Dec 7, 2019, at 1:43 PM, Jimmy Gauvin <jimmy.gau...@gmail.com> wrote: > > Hi, > > The first vocabulary is full of information. So much so that it is easy to > overlook lots of "tasty tidbits". > The answer your question " where is that first explained to the J Beginner > ? " , it is not so much explained but rather demonstrated. > I had to change my reading style from "passive assimilation of information" > to "active comprehension of the text and its implications". > > Some tidbits are never repeated (due to Roger's preference for conciseness > [this being pure speculation]). > > For example, one day I was looking for the equivalent of APL's expand > function: > 1 0 1 0 1 0 0 1\1 2 3 4 > 1 0 2 0 3 0 0 4 > > This is tucked away as a note in : > https://www.jsoftware.com/help/dictionary/d202n.htm > > 6. The following cases merit special mention: > p:^:_1 n gives the number of primes less than n, denoted by π(n) in math > q:^:_1 is */ > > b&#^:_1 where b is a boolean list is Expand (whose fill atom f can be > specified by fit, b&#^:_1!.f or #^:_1!.f ) > > a&#.^:_1 produces the base-a representation > !^:_1 and !&n^:_1 and n&!^:_1 produce the appropriate results > {= and i."1&1 are inverses of each other; these convert between integer > permutation vectors and boolean permutation matrices > > On Sat, Dec 7, 2019 at 1:18 PM 'Jim Russell' via Programming < > programm...@jsoftware.com> wrote: > >> As shown throughout the Vocabulary. >> But where is that first explained to the J Beginner? >> >>> On Dec 7, 2019, at 1:08 PM, Jimmy Gauvin <jimmy.gau...@gmail.com> wrote: >>> >>> Hi, >>> >>> note also that the shape of the results can vary considerably : >>> >>> 1 2 3 (+ ; * ; - ; +/ ; ,&4 5) 6 7 8 >>> ┌──────┬───────┬────────┬───────┬─────────────────┐ >>> │7 9 11│6 14 24│_5 _5 _5│7 8 9│6 7 8 4 5 0 0 0 0│ >>> │ │ │ │8 9 10│6 7 8 4 5 4 5 0 0│ >>> │ │ │ │9 10 11│6 7 8 4 5 4 5 4 5│ >>> └──────┴───────┴────────┴───────┴─────────────────┘ >>> >>> >>> >>> On Sat, Dec 7, 2019 at 10:23 AM 'Jim Russell' via Programming < >>> programm...@jsoftware.com> wrote: >>> >>>> Lovely! Not at all obvious (to me)until you do it with simple verbs. >>>> >>>>> On Dec 7, 2019, at 9:30 AM, Jimmy Gauvin <jimmy.gau...@gmail.com> >> wrote: >>>>> >>>>> Hi, >>>>> >>>>> is the following what you want ? >>>>> >>>>> 1 2 3 (+ ; * ; -) 6 7 8 >>>>> ┌──────┬───────┬────────┐ >>>>> │7 9 11│6 14 24│_5 _5 _5│ >>>>> └──────┴───────┴────────┘ >>>>> >>>> >>> ---------------------------------------------------------------------- >>> 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
