De Bruijn sequences: Difference between revisions
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=={{header|REXX}}== |
=={{header|REXX}}== |
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The de Bruijn sequence generated by |
The de Bruijn sequence generated by these REXX programs are identical to the sequence shown on the ''discussion'' page (1<sup>st</sup> topic). |
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=== hard-coded node to be removed === |
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<br>''not'' be added to the sequence. |
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<lang rexx>/*REXX pgm calculates the de Bruijn sequence for all pin numbers (4 digit decimals). */ |
<lang rexx>/*REXX pgm calculates the de Bruijn sequence for all pin numbers (4 digit decimals). */ |
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$= /*initialize the de Bruijn sequence. */ |
$= /*initialize the de Bruijn sequence. */ |
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──────── 4 errors found. |
──────── 4 errors found. |
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</pre> |
</pre> |
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=== programmatically removing of a node === |
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This method slightly bloats the program and slows execution. |
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<lang rexx>/*REXX pgm calculates the de Bruijn sequence for all pin numbers (4 digit decimals). */ |
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$= /*initialize the de Bruijn sequence. */ |
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/* ··· is skipped near the cycle end. */ |
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do j=0 for 10; $= $ j; jj= j || j /*compose the left half of the numbers.*/ |
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$$= space($, 0) /* [↓] " right " " " " */ |
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do k=jj+1 to 99; z= jj || right(k, 2, 0) |
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if pos(z, $$)\==0 then iterate /*# in sequence? Skip it*/ |
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$= $ z /* ◄─────────────────────────────────┐ */ |
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end /*k*/ /*append a number to the sequence──◄─┘ */ |
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$$= space($, 0) |
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do r= jj to (j || 9); b= right(r, 2, 0) /*compose the left half of the numbers.*/ |
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if b==jj then iterate |
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$= $ right(b, 2, 0) /* [↓] " right " " " " */ |
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$$= space($, 0); do k= b+1 to 99; z= right(b, 2, 0) || right(k, 2, 0) |
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if pos(z, $$)\==0 then iterate /*# in sequence? Skip it*/ |
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$= $ z /* ◄─────────────────────────────────┐ */ |
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end /*k*/ /*append a number to the sequence──◄─┘ */ |
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$$= space($, 0) |
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end /*r*/ |
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end /*j*/ |
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$= delword($, words($)-4, 1) /*delete 5th from the last word in $. */ |
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$= space($, 0) |
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@deB= 'de Bruijn sequence' /*literal used in some SAY instructions*/ |
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$= $ || left($, 3) /*append 000*/ /*simulate "wrap-around" de Bruijn seq.*/ |
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say 'length of the' @deB " is " length($) /*display the length of de Bruijn seq.*/ |
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say; say 'first 130 digits of the' @deB":" /*display the title for the next line. */ |
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say left($, 130) /*display 130 left-most digits of seq. */ |
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say; say ' last 130 digits of the' @deB":" /*display the title for the next line. */ |
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say right($, 130) /*display 130 right-most digits of seq.*/ |
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call val $ /*call the VAL sub for verification. */ |
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@deB= 'reversed' @deB /*next, we'll check on a reversed seq.*/ |
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$r= reverse($) /*do what a mirror does, reversify it.*/ |
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call val $r /*call the VAL sub for verification. */ |
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$= overlay(., $, 4444) /*replace 4,444th digit with a period. */ |
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@deB= 'overlaid' subword(@deB, 2) /* [↑] this'll cause a validation barf.*/ |
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call val $ /*call the VAL sub for verification. */ |
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exit /*stick a fork in it, we're all done. */ |
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/*──────────────────────────────────────────────────────────────────────────────────────*/ |
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val: parse arg $$$; e= 0; _= copies('─',8) /*count of errors (missing PINs) so far*/ |
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say; say _ 'validating the' @deB"." /*display what's happening in the pgm. */ |
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do pin=0 for 1e4; pin4= right(pin,4,0) /* [↓] maybe add leading zeros to pin.*/ |
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if pos(pin4, $$$)\==0 then iterate /*Was number found? Just as expected. */ |
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say 'PIN number ' pin " wasn't found in" @deb'.' |
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e= e + 1 /*bump the counter for number of errors*/ |
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end /*pin*/ /* [↑] validate all 10,000 pin numbers*/ |
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if e==0 then e= 'No' /*Gooder English (sic) the error count.*/ |
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say _ e 'errors found.' /*display the number of errors found. */ |
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return</lang> |
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{{out|output|text= is identical to the 1<sup>st</sup> REXX version.}} <br><br> |
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