Anti-primes: Difference between revisions
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m →{{header|REXX}}: changed title comment. |
→{{header|REXX}}: added a faster 2nd REXX version. |
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=={{header|REXX}}== |
=={{header|REXX}}== |
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===even and odd numbers=== |
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<!-- This REXX version does what the Rosetta Code task requires. Note that the first DO loop is fixed at 59, but the second DO loop if open-ended. Please read/observe the entire REXX program before flagging as incorrect. --- Gerard Schildberger. ~--> |
<!-- This REXX version does what the Rosetta Code task requires. Note that the first DO loop is fixed at 59, but the second DO loop if open-ended. Please read/observe the entire REXX program before flagging as incorrect. --- Gerard Schildberger. ~--> |
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55 61261200 |
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</pre> |
</pre> |
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===only even numbers=== |
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This REXX version only processes ''even'' numbers (unity is treated as a special case.) |
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It's about '''10%''' faster than the 1<sup>st</sup> REXX version. |
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<lang rexx>/*REXX program finds and displays N number of anti─primes or highly─composite numbers.*/ |
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parse arg N . /*obtain optional argument from the CL.*/ |
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if N=='' | N=="," then N=20 /*Not specified? Then use the default.*/ |
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@.=.; @.1= 1; @.2= 2; @.4= 3; @.5= 2; @.6= 4 |
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say '─index─ ──anti─prime──' /*display a title for the numbers shown*/ |
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#= 1 /*the count of anti─primes found " " */ |
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maxD= 1 /*the maximum number of divisors so far*/ |
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say center(#, 7) right(1, 10) /*display the index and the anti─prime.*/ |
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do once=1 for 1 |
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do i=2 by 2 to 59 /*step through possible numbers by twos*/ |
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d= #divs(i); if d<=maxD then iterate /*get # divisors; Is too small? Skip.*/ |
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#= # + 1; maxD= d /*found an anti─prime #; set new minD.*/ |
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say center(#, 7) right(i, 10) /*display the index and the anti─prime.*/ |
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if #>=N then leave once /*if we have enough anti─primes, done. */ |
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end /*i*/ |
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do j=60 by 20 /*step through possible numbers by 20. */ |
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d= #divs(j); if d<=maxD then iterate /*get # divisors; Is too small? Skip.*/ |
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#= # + 1; maxD= d /*found an anti─prime #; set new minD.*/ |
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say center(#, 7) right(j, 10) /*display the index and the anti─prime.*/ |
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if #>=N then leave once /*if we have enough anti─primes, done. */ |
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end /*j*/ |
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end /*once*/ |
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exit /*stick a fork in it, we're all done. */ |
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/*──────────────────────────────────────────────────────────────────────────────────────*/ |
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#divs: parse arg x; if @.x\==. then return @.x /*if pre─computed, then return shortcut*/ |
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$= 3; y= x%2 |
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/* [↑] start with known num of Pdivs.*/ |
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do k=3 for x%2-3 while k<y |
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if x//k==0 then do /*if no remainder, then found a divisor*/ |
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$=$+2; y=x%k /*bump $ Pdivs, calculate limit Y. */ |
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if k>=y then do; $= $-1; leave; end /*limit?*/ |
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end /* ___ */ |
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else if k*k>x then leave /*only divide up to √ x */ |
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end /*k*/ /* [↑] this form of DO loop is faster.*/ |
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return $+1 /*bump "proper divisors" to "divisors".*/</lang> |
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{{out|output|text= is identical to the 1<sup>st</sup> REXX version.}} <br><br> |
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=={{header|Sidef}}== |
=={{header|Sidef}}== |
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