Rosetta Code

Run-length encoding: Difference between revisions

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Run-length encoding (view source)

Revision as of 21:10, 9 November 2009

182 bytes removed ,  14 years ago
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Line 368:
 
=={{header|Common Lisp}}==
<lang lisp>(defun group-similarencode (sequence &key (test 'eql)word)
(labels ((rec (word len pos chr count acc)
(loop for x in (rest sequence)
with temp (cond ((= pos len) (subseqacons sequencechr 0count 1acc))
((char= chr (char word pos)) (rec word len (1+ pos) chr (1+ count) acc))
if (funcall test (first temp) x)
(t (rec word len (1+ pos) (char word pos) 1 (firstacons chr count elemacc))))))▼
do (push x temp)
(cdr (nreverse (rec word (length word) 0 #\null 1 nil)))))
else▼
collect temp
and do (setf temp (list x))))
 
(defun run-length-encodedecode (sequencealist)
(if (null alist)
(mapcar (lambda (group) (list (first group) (length group)))
▲ else""
(group-similar (coerce sequence 'list))))
(destructuring-bind (chr . count) (car alist)
(format nil "~A~A" (make-string count :initial-element chr) (decode (cdr alist))))))
 
(run-length-encode "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW")▼
(defun run-length-decode (sequence)
(run-length-decode '((#\W 12) (#\B 1) (#\W 12) (#\B 3) (#\W 24) (#\B 1)))</lang>▼
(reduce (lambda (s1 s2) (concatenate 'simple-string s1 s2))
(mapcar (lambda (elem)
(make-string (second elem)
:initial-element
▲ (first elem)))
sequence)))
 
▲(run-length-encode "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW")
▲(run-length-decode '((#\W 12) (#\B 1) (#\W 12) (#\B 3) (#\W 24) (#\B 1)))</lang>
 
=={{header|D}}==
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