Additive primes: Difference between revisions
Content added Content deleted
m (→{{header|REXX}}: changed the GENP subroutine.) |
(→{{header|REXX}}: added/changed whitespace and comments, optimized the program.) |
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call genP n /*generate all primes under N. */ |
call genP n /*generate all primes under N. */ |
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w= 10 /*width of a number in any column. */ |
w= 10 /*width of a number in any column. */ |
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title= " additive primes that are < " n |
title= " additive primes that are < " commas(n) |
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if cols>0 then say ' index │'center(title, 1 + cols*(w+1) ) |
if cols>0 then say ' index │'center(title, 1 + cols*(w+1) ) |
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if cols>0 then say '───────┼'center("" , 1 + cols*(w+1), '─') |
if cols>0 then say '───────┼'center("" , 1 + cols*(w+1), '─') |
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found= 0; idx= 1 /*initialize # of additive primes & IDX*/ |
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$= /*a list of additive primes (so far). */ |
$= /*a list of additive primes (so far). */ |
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do j= |
do j=1 for #; p= @.j /*obtain the Jth prime. */ |
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_= sumDigs( |
_= sumDigs(p); if \!._ then iterate /*is sum of J's digs a prime? No, skip.*/ /* ◄■■■■■■■■ a filter. */ |
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found= found + 1 /*bump the count of additive primes. */ |
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if cols<0 then iterate /*Build the list (to be shown later)? */ |
if cols<0 then iterate /*Build the list (to be shown later)? */ |
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c= commas( |
c= commas(p) /*maybe add commas to the number. */ |
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$= $ right(c, max(w, length(c) ) ) |
$= $ right(c, max(w, length(c) ) ) /*add additive prime──►list, allow big#*/ |
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if |
if found//cols\==0 then iterate /*have we populated a line of output? */ |
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say center(idx, 7)'│' substr($, 2); $= /*display what we have so far (cols). */ |
say center(idx, 7)'│' substr($, 2); $= /*display what we have so far (cols). */ |
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idx= idx + cols /*bump the index count for the output*/ |
idx= idx + cols /*bump the index count for the output*/ |
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if cols>0 then say '───────┴'center("" , 1 + cols*(w+1), '─') |
if cols>0 then say '───────┴'center("" , 1 + cols*(w+1), '─') |
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say |
say |
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say 'found ' commas( |
say 'found ' commas(found) title |
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exit 0 /*stick a fork in it, we're all done. */ |
exit 0 /*stick a fork in it, we're all done. */ |
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/*──────────────────────────────────────────────────────────────────────────────────────*/ |
/*──────────────────────────────────────────────────────────────────────────────────────*/ |
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sumDigs: parse arg x 1 s 2; do k=2 for length(x)-1; s= s + substr(x,k,1); end; return s |
sumDigs: parse arg x 1 s 2; do k=2 for length(x)-1; s= s + substr(x,k,1); end; return s |
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/*──────────────────────────────────────────────────────────────────────────────────────*/ |
/*──────────────────────────────────────────────────────────────────────────────────────*/ |
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genP: parse arg n; |
genP: parse arg n; @.1= 2; @.2= 3; @.3= 5; @.4= 7; @.5= 11; @.6= 13 |
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!.= 0; !.2= 1; !.3= 1; !.5= 1; !.7= 1; !.11= 1; !.13= 1 |
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#= 6; sq.#= @.# ** 2 /*the number of primes; prime squared.*/ |
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do j=@.#+2 by 2 for max(0, n%2-@.#%2-1) /*find odd primes from here on. */ |
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parse var j '' -1 _ /*obtain the last digit of the J var.*/ |
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if _==5 then iterate; if j// 3==0 then iterate /*J ÷ by 5? J ÷ by 3? */ |
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if j// 7==0 then iterate; if j//11==0 then iterate /*" " " 7? " " " 11? */ |
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/* [↓] divide by the primes. ___ */ |
/* [↓] divide by the primes. ___ */ |
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do k=6 while sq.k<=j /*divide J by other primes ≤ √ J */ |
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if j//@.k==0 then iterate j /*÷ by prev. prime? ¬prime ___ */ |
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end /*k*/ /* [↑] only divide up to √ J */ |
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#= # + 1; @.#= j; sq.#= j*j; !.j= 1 /*bump prime count; assign prime & flag*/ |
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end /*j*/; return</lang> |
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{{out|output|text= when using the default inputs:}} |
{{out|output|text= when using the default inputs:}} |
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<pre> |
<pre> |
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