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June 2018 Update

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Ingy döt Net 2018-06-22 20:57:24 +00:00
parent ba8067c3b7
commit 22f33d4004
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22
Task/LZW-compression/REXX/lzw-compression-2.rexx
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@ -1,31 +1,29 @@
/*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
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.*/
say 'reconstituted=' LZWd(cypher)
say ' LZW integers=' cypher
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 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)
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*/
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)
else if _==# then ?=w || left(w, 1)
$=$ || ?
@.#=w || left(?, 1); #=#+1
w=?
@.#=w || left(?, 1); #=#+1; w=?
end /*k*/
return $