Gotcha! ([EMAIL PROTECTED]&.(p:^:_1)@>: >./@: (<.&.^.) ])"0[ 25 23 fpp 25 25 25 2 5 2
which means that fpp does the following a) if input is prime -> return prime b) if not, find if it is a prime power -> return the base prime and the power c) if not keep incrementing (only odd numbers considered) -> until (a) or (b) is satisfied. Question was if (b) & (c) can be programmed tacitly. As it stands, your solution of finding the nearest prime is already available as a library function _4 p: _4 p: 25 23 _4 p: 25 + i.20 23 23 23 23 23 29 29 31 31 31 31 31 31 37 37 37 37 41 41 43 _4 p: 160+i.20 157 157 157 157 163 163 163 163 167 167 167 167 167 167 173 173 173 173 173 173 Regards, Yuva On 9/21/06, R.E. Boss <[EMAIL PROTECTED]> wrote:
([EMAIL PROTECTED]&.(p:^:_1)@>: >./@([^ <[EMAIL PROTECTED]) ])"0[160+i.20 157 157 157 163 163 163 163 167 167 169 169 169 169 173 173 173 173 173 173 179 [EMAIL PROTECTED]&.(p:^:_1)@>: NB. Hui's solution, excluding the first (2) <[EMAIL PROTECTED] NB. floor of prime log y >./@([^ <[EMAIL PROTECTED]) NB. maximum of prime ^ floor of prime ^. y Since ^. and ^ are inverse of each other it can be reformulated to ([EMAIL PROTECTED]&.(p:^:_1)@>: >./@: (<.&.^.) ])"0[160+i.20 157 157 157 163 163 163 163 167 167 167 167 167 167 173 173 173 173 173 173 179 R.E. BOSS -----Oorspronkelijk bericht----- Van: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Namens Yuvaraj Athur Raghuvir Verzonden: donderdag 21 september 2006 6:35 Aan: Programming forum Onderwerp: Re: [Jprogramming] Explicit to Tacit - newbie question Hello, Putting together the previous mails, I have written my first J program to find the nearest prime or prime power to a number. Here I am excluding powers of 2. Hurrah!! I could move quite far until I had to loop that incremented and applied the logic. Program follows. Can fpp be tacitly defined? Regards, Yuva J Program: NB. find the nearest prime or prime power for a number NB. odd means remainder is 1 o =: 2&| NB. makeodd: - use tie + agenda (for implementing if condition!) mo =: (>: ` ]) @. o NB. whole: compare with Floor of number w =: ]=<. NB. pl: list of primes less that given number pl =: i. &. (p:^:_1) NB. use of dual operator &. (Henry Rich) NB. however, I need primes <= number ple=: pl@>: NB. add one more and get the list! (Roger Hui) NB. check if the we have found a suitable base prime ckl =. w @: (ple ^. ]) NB. ckl: Check the log wrt primes list d =: +/ @: ckl NB. done: stopping condition NB. repeat the discovery by increasing the value fpp =: 3 : 0 k =. mo y while. (0 = d k) do. k =. 2&+k end. j =. I. ckl k t =. p:j y,k, j , t , t ^. k ) On 9/21/06, Roger Hui <[EMAIL PROTECTED]> wrote: > > ple=: i.&.(p:^:_1)@>: > ple 30 > 2 3 5 7 11 13 17 19 23 29 > ple 31 > 2 3 5 7 11 13 17 19 23 29 31 > ple 32 > 2 3 5 7 11 13 17 19 23 29 31 > > Or, alternatively, > > ple=: pl@>: > > where pl is what you have already defined. > > > > ----- Original Message ----- > From: Yuvaraj Athur Raghuvir <[EMAIL PROTECTED]> > Date: Wednesday, September 20, 2006 8:30 pm > Subject: Re: [Jprogramming] Explicit to Tacit - newbie question > > > Thanks! > > > > Interesting use of the dual/under operator &. Although I had > > studied the > > form, this usage didnot occur to me! > > > > As an extension question: > > > > p1 =: i. &. (p:^:_1) NB. primes strictly less than number > > > > so, > > p1 37 > > 2 3 5 7 11 13 17 19 23 29 31 > > > > In the generated list, I want the number included if it is prime. > > What would > > that extension be using &. ? > > Or, does that need compelete verb definition? > > > ---------------------------------------------------------------------- > 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
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