Substring primes: Difference between revisions
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m (→{{header|REXX}}: changed comments and some variable names.) |
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say ' index │'center(title, 1 + cols*(w+1) ) /*display the title of the output. */ |
say ' index │'center(title, 1 + cols*(w+1) ) /*display the title of the output. */ |
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say '───────┼'center("" , 1 + cols*(w+1), '─') /* " " separator " " " */ |
say '───────┼'center("" , 1 + cols*(w+1), '─') /* " " separator " " " */ |
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found= 0; |
found= 0; idx= 1 /*define # substring primes found; IDX.*/ |
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$= /*a list of substring primes (so far). */ |
$= /*a list of substring primes (so far). */ |
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do j=1 for #; |
do j=1 for #; p= @.j; p2= substr(p, 2) /*search for primes that fit criteria. */ |
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if verify( |
if verify(p, 014689, 'M')>0 then iterate /*does it contain any of these digits? */ |
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if verify( |
if verify(p2, 25 , 'M')>0 then iterate /* " P2 " " " " " */ |
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L= length( |
L= length(p) /*obtain the length of the P prime.*/ |
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do k=1 for L-1 /*test for primality for all substrings*/ |
do k=1 for L-1 /*test for primality for all substrings*/ |
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do m=k+1 to L; y= substr( |
do m=k+1 to L; y= substr(p, k, m-1) /*extract a substring from the P prime.*/ |
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if \!.y then iterate j /*does substring of |
if \!.y then iterate j /*does substring of P not prime? Skip.*/ |
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end /*m*/ |
end /*m*/ |
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end /*k*/ |
end /*k*/ |
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found= found + 1 /*bump the number of substring primes. */ |
found= found + 1 /*bump the number of substring primes. */ |
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$= $ right( commas( |
$= $ right( commas(p), w) /*add a substring prime ──► $ list. */ |
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if found//cols\==0 then iterate /*have we populated a line of output? */ |
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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#=5; s.#= @.# **2 /*number of primes so far; prime². */ |
#=5; s.#= @.# **2 /*number of primes so far; prime². */ |
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/* [↓] generate more primes ≤ high.*/ |
/* [↓] generate more primes ≤ high.*/ |
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do j=@.#+2 by 2 to n |
do j=@.#+2 by 2 to n-1 /*find odd primes from here on. */ |
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parse var j '' -1 _; |
parse var j '' -1 _; if _==5 then iterate /*J ÷ by 5? (right digit)*/ |
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if j//3==0 then iterate; if j//7==0 then iterate /*" " " 3?; J ÷ by 7? */ |
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if j// 7==0 then iterate /*" " " 7? */ |
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do k=5 while s.k<=j /* [↓] divide by the known odd primes.*/ |
do k=5 while s.k<=j /* [↓] divide by the known odd primes.*/ |
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if j // @.k == 0 then iterate j /*Is J ÷ X? Then not prime. ___ */ |
if j // @.k == 0 then iterate j /*Is J ÷ X? Then not prime. ___ */ |
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end /*k*/ /* [↑] only process numbers ≤ √ J */ |
end /*k*/ /* [↑] only process numbers ≤ √ J */ |
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#= #+1; @.#= j; s.#= j*j; !.j= 1 /*bump # of Ps; assign next P; P²; P# */ |
#= #+1; @.#= j; s.#= j*j; !.j= 1 /*bump # of Ps; assign next P; P²; P# */ |
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end /*j*/; return</lang> |
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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index │ primes (base ten) where all substrings are also primes, where N < 500 |
index │ primes (base ten) where all substrings are also primes, where N < 500 |
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───────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────── |
───────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────── |
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1 │ |
1 │ 2 3 5 7 23 37 53 73 373 |
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───────┴─────────────────────────────────────────────────────────────────────────────────────────────────────────────── |
───────┴─────────────────────────────────────────────────────────────────────────────────────────────────────────────── |
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