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2016 Update

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Tina Müller 2016-12-05 22:15:40 +01:00
parent 948b86eafa
commit dcf5d15da3
7965 changed files with 139854 additions and 31002 deletions
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61
Task/LZW-compression/REXX/lzw-compression-2.rexx
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@ -1,32 +1,31 @@
/*REXX pgm compresses text using LZW (Lempel-Ziv-Welch), and reconstitutes it.*/
parse arg x /*get an optional argument from the CL.*/
if x=='' then x='"There is nothing permanent except change." ─── Heraclitus [540-475 BC]'
say 'original text=' x
cypher=LZWc(x) /*compress text using the LZW algorithm*/
say 'reconstituted=' LZWd(cypher)
say ' LZW integers=' cypher /*also display the LZW integers used. */
exit /*stick a fork in it, we're all done. */
/*────────────────────────────────────────────────────────────────────────────*/
LZWc: procedure; parse arg y,,w $ @.; #=256 /*the LZW compress algorithm.*/
do j=0 for 256; _=d2c(j); @._=j; end /*j*/
/*REXX program compresses text using the LZW (Lempel─Ziv─Welch), and reconstitutes it.*/
parse arg x /*get an optional argument from the CL.*/
if x=='' then x= '"There is nothing permanent except change." ─── Heraclitus [540-475 BC]'
say 'original text=' x
cypher=LZWc(x) /*compress text using the LZW algorithm*/
say; say 'reconstituted=' LZWd(cypher) /*display the original cypher text. */
say; say ' LZW integers=' cypher /*also display the LZW integers used.*/
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
LZWc: procedure; parse arg y,,w $ @.; #=256 /*the LZW compress algorithm.*/
do j=0 for #; _=d2c(j); @._=j; end /*j*/
do k=1 for length(y); _=w || substr(y,k,1)
if @._=='' then do; $=$ @.w
@._=#; #=#+1
w=substr(y,k,1)
end
else w=_
end /*k*/
return strip($ @.w) /*remove any superfluous blanks*/
/*────────────────────────────────────────────────────────────────────────────*/
LZWd: procedure; parse arg w y,,@.; #=256 /*the LZW decompress algorithm.*/
do j=0 for 256; @.j=d2c(j); end /*j*/
$=@.w; w=$
do k=1 for words(y); _=word(y,k)
if @._\=='' | @.k==' ' then ?=@._
else if _=# then ?=w || left(w,1)
$=$ || ?
@.#=w || left(?,1); #=#+1
w=?
end /*k*/
return $
do k=1 for length(y); _=w || substr(y, k, 1)
if @._=='' then do; $=$ @.w; @._=#; #=#+1
w=substr(y, k, 1)
end
else w=_
end /*k*/
return strip($ @.w) /*remove any superfluous blanks*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
LZWd: procedure; parse arg w y,,@.; #=256 /*the LZW decompress algorithm.*/
do j=0 for #; @.j=d2c(j); end /*j*/
$=@.w; w=$
do k=1 for words(y); _=word(y, k)
if @._\=='' | @.k==" " then ?=@._
else if _=# then ?=w || left(w, 1)
$=$ || ?
@.#=w || left(?, 1); #=#+1
w=?
end /*k*/
return $