Rosetta Code

Sequence of primes by trial division: Difference between revisions

Page Discussion

Sequence of primes by trial division (view source)

Revision as of 20:19, 2 December 2015

18 bytes added ,  8 years ago
m
→‎more optimized: added/changed whitespace and comments.
(→‎{{header|EchoLisp}}: rmv extra whitespace around subsections)
m (→‎more optimized: added/changed whitespace and comments.)
Line 1,011:
if n=='' then n=26 /*Not specified? Then assume default.*/
tell=n>0; n=abs(n) /*N is negative? Then don't display. */
@.1=2; @.2=3; @.3=5; @.4=7; @.5=11; @.6=13; #=5; s=@.#+2
/* [↑] is the number of low primes. */
do p=1 for # while p<=n /* [↓] find primes, but don't show 'em*/
if tell then say right(@.p, 9) /*display some pre-defined low primes. */
!.p=@.p**2 /*also compute the squared value of P. */
end /*p*/ /* [↑] allows faster loop (below). */
/* [↓] N: default lists up to 101 #s.*/
do j=s by 2 while #<n /*startcontinue on with the next odd prime. */
if j// 3 ==0 then iterate /*is this numberinteger a triple? multiple of three? */
parse var j '' -1 _ /*obtain the last digit of the J var.*/
if _ ==5 then iterate /*is this numberinteger a nickel? multiple of five? */
if j// 7 ==0 then iterate /* " " " lucky? " " " seven? */
if j// 11 ==0 then iterate /* " " " a multiple of" 11? " " eleven?*/
/* [↓] divide by the primes. ___ */
do k=p to # while !.k<=j /*divide J by other primes ≤ √ J */
if j//@.k==0 then iterate j /*+÷ by prev. prime? ¬prime ___ */
end /*jk*/ /* [↑] only divide up to √ J */
#=#+1 /*bump the countercount of number of primes. */
@.#=j; !.#=j*j /*define this prime; define its square.*/
if tell then say right(j, 9) /*maybe display this prime ──► terminal*/
end /*j*/ /*j*/ /* [↑] only display N number of primes*/
/* [↓] display number of primes found.*/
say # ' primes found.' /*stick a fork in it, we're all done. */</lang>
'''output''' &nbsp; is the same as the 1<sup>st</sup> REXX version. <br>
 
Retrieved from "https://rosettacode.org/wiki/Special:MobileDiff/250152"