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Revision 1.12.28.1 - (hide annotations)
Tue Mar 24 11:44:20 2009 UTC (5 years ago) by rtoy
Branch: unicode-utf16-branch
CVS Tags: unicode-utf16-char-support-2009-03-26, unicode-utf16-char-support-2009-03-25
Changes since 1.12: +27 -3 lines
Compare strings using code-point order, since we don't have any kind
of collation support.
1 ram 1.1 ;;; -*- Log: code.log; Package: Lisp -*-
2     ;;;
3     ;;; **********************************************************************
4 ram 1.3 ;;; This code was written as part of the CMU Common Lisp project at
5     ;;; Carnegie Mellon University, and has been placed in the public domain.
6     ;;;
7     (ext:file-comment
8 rtoy 1.12.28.1 "$Header: /tiger/var/lib/cvsroots/cmucl/src/code/string.lisp,v 1.12.28.1 2009/03/24 11:44:20 rtoy Exp $")
9 ram 1.3 ;;;
10 ram 1.1 ;;; **********************************************************************
11     ;;;
12 pw 1.11 ;;; Functions to implement strings for CMU Common Lisp
13 ram 1.1 ;;; Written by David Dill
14 ram 1.4 ;;; Rewritten by Skef Wholey, Bill Chiles and Rob MacLachlan.
15 ram 1.1 ;;;
16     ;;; ****************************************************************
17     ;;;
18 ram 1.4 (in-package "LISP")
19 ram 1.1 (export '(char schar string
20     string= string-equal string< string> string<= string>= string/=
21     string-lessp string-greaterp string-not-lessp string-not-greaterp
22     string-not-equal
23     make-string
24     string-trim string-left-trim string-right-trim
25     string-upcase
26     string-downcase string-capitalize nstring-upcase nstring-downcase
27     nstring-capitalize))
28    
29    
30     (defun string (X)
31     "Coerces X into a string. If X is a string, X is returned. If X is a
32     symbol, X's pname is returned. If X is a character then a one element
33     string containing that character is returned. If X cannot be coerced
34     into a string, an error occurs."
35     (cond ((stringp x) x)
36     ((symbolp x) (symbol-name x))
37     ((characterp x)
38     (let ((res (make-string 1)))
39     (setf (schar res 0) x) res))
40     (t
41 pw 1.11 (error 'simple-type-error
42     :datum x
43     :expected-type '(or string symbol character)
44     :format-control "~S cannot be coerced to a string."
45     :format-arguments (list x)))))
46 ram 1.1
47     ;;; With-One-String is used to set up some string hacking things. The keywords
48     ;;; are parsed, and the string is hacked into a simple-string.
49    
50     (eval-when (compile)
51    
52     (defmacro with-one-string (string start end cum-offset &rest forms)
53 ram 1.4 `(let ((,string (if (stringp ,string) ,string (string ,string))))
54 pw 1.10 ;; Optimizer may prove STRING is one.
55     (declare (optimize (ext:inhibit-warnings 3)))
56 ram 1.4 (with-array-data ((,string ,string :offset-var ,cum-offset)
57     (,start ,start)
58     (,end (or ,end (length (the vector ,string)))))
59     ,@forms)))
60 ram 1.1
61     )
62    
63     ;;; With-String is like With-One-String, but doesn't parse keywords.
64    
65     (eval-when (compile)
66    
67     (defmacro with-string (string &rest forms)
68 ram 1.4 `(let ((,string (if (stringp ,string) ,string (string ,string))))
69     (with-array-data ((,string ,string)
70     (start)
71     (end (length (the vector ,string))))
72     ,@forms)))
73 ram 1.1
74     )
75    
76     ;;; With-Two-Strings is used to set up string comparison operations. The
77     ;;; keywords are parsed, and the strings are hacked into simple-strings.
78    
79     (eval-when (compile)
80    
81     (defmacro with-two-strings (string1 string2 start1 end1 cum-offset-1
82     start2 end2 &rest forms)
83 ram 1.4 `(let ((,string1 (if (stringp ,string1) ,string1 (string ,string1)))
84     (,string2 (if (stringp ,string2) ,string2 (string ,string2))))
85     (with-array-data ((,string1 ,string1 :offset-var ,cum-offset-1)
86     (,start1 ,start1)
87     (,end1 (or ,end1 (length (the vector ,string1)))))
88     (with-array-data ((,string2 ,string2)
89     (,start2 ,start2)
90     (,end2 (or ,end2 (length (the vector ,string2)))))
91     ,@forms))))
92 ram 1.1
93     )
94 wlott 1.2
95 ram 1.1
96     (defun char (string index)
97     "Given a string and a non-negative integer index less than the length of
98     the string, returns the character object representing the character at
99     that position in the string."
100 ram 1.4 (declare (optimize (safety 1)))
101 ram 1.1 (char string index))
102    
103     (defun %charset (string index new-el)
104 ram 1.4 (declare (optimize (safety 1)))
105 ram 1.1 (setf (char string index) new-el))
106    
107     (defun schar (string index)
108     "SCHAR returns the character object at an indexed position in a string
109     just as CHAR does, except the string must be a simple-string."
110 ram 1.4 (declare (optimize (safety 1)))
111 ram 1.1 (schar string index))
112    
113     (defun %scharset (string index new-el)
114 ram 1.4 (declare (optimize (safety 1)))
115 ram 1.1 (setf (schar string index) new-el))
116    
117     (defun string=* (string1 string2 start1 end1 start2 end2)
118 ram 1.4 (with-two-strings string1 string2 start1 end1 offset1 start2 end2
119     (not (%sp-string-compare string1 start1 end1 string2 start2 end2))))
120 ram 1.1
121    
122     (defun string/=* (string1 string2 start1 end1 start2 end2)
123 ram 1.4 (with-two-strings string1 string2 start1 end1 offset1 start2 end2
124     (let ((comparison (%sp-string-compare string1 start1 end1
125     string2 start2 end2)))
126     (if comparison (- (the fixnum comparison) offset1)))))
127 ram 1.1
128     (eval-when (compile eval)
129    
130     ;;; Lessp is true if the desired expansion is for string<* or string<=*.
131     ;;; Equalp is true if the desired expansion is for string<=* or string>=*.
132     (defmacro string<>=*-body (lessp equalp)
133     (let ((offset1 (gensym)))
134 ram 1.4 `(with-two-strings string1 string2 start1 end1 ,offset1 start2 end2
135     (let ((index (%sp-string-compare string1 start1 end1
136     string2 start2 end2)))
137     (if index
138 ram 1.8 (cond ((= (the fixnum index) (the fixnum end1))
139     ,(if lessp
140     `(- (the fixnum index) ,offset1)
141     `nil))
142     ((= (+ (the fixnum index) (- start2 start1))
143     (the fixnum end2))
144     ,(if lessp
145     `nil
146 rtoy 1.12.28.1 `(- (the fixnum index) ,offset1)))
147     #-unicode
148 ram 1.4 ((,(if lessp 'char< 'char>)
149     (schar string1 index)
150     (schar string2 (+ (the fixnum index) (- start2 start1))))
151     (- (the fixnum index) ,offset1))
152 rtoy 1.12.28.1 #-unicode
153     (t nil)
154     #+unicode
155     (t
156     ;; Compare in code point order. See
157     ;; http://icu-project.org/docs/papers/utf16_code_point_order.html
158     (flet ((fixup (code)
159     (if (>= code #xe000)
160     (- code #x800)
161     (+ code #x2000))))
162     (declare (inline fixup))
163     (let* ((c1 (char-code (schar string1 index)))
164     (c2 (char-code (schar string2 (+ (the fixnum index) (- start2 start1))))))
165     (cond ((and (>= c1 #xd800)
166     (>= c2 #xd800))
167     (let ((fix-c1 (fixup c1))
168     (fix-c2 (fixup c2)))
169     (if (,(if lessp '< '>) fix-c1 fix-c2)
170     (- (the fixnum index) ,offset1)
171     nil)))
172     (t
173     (if (,(if lessp '< '>) c1 c2)
174     (- (the fixnum index) ,offset1)
175     nil)))))))
176 ram 1.4 ,(if equalp `(- (the fixnum end1) ,offset1) 'nil))))))
177 ram 1.1 ) ; eval-when
178    
179     (defun string<* (string1 string2 start1 end1 start2 end2)
180     (declare (fixnum start1 start2))
181     (string<>=*-body t nil))
182    
183     (defun string>* (string1 string2 start1 end1 start2 end2)
184     (declare (fixnum start1 start2))
185     (string<>=*-body nil nil))
186    
187     (defun string<=* (string1 string2 start1 end1 start2 end2)
188     (declare (fixnum start1 start2))
189     (string<>=*-body t t))
190    
191     (defun string>=* (string1 string2 start1 end1 start2 end2)
192     (declare (fixnum start1 start2))
193     (string<>=*-body nil t))
194    
195    
196    
197     (defun string< (string1 string2 &key (start1 0) end1 (start2 0) end2)
198     "Given two strings, if the first string is lexicographically less than
199     the second string, returns the longest common prefix (using char=)
200     of the two strings. Otherwise, returns ()."
201     (string<* string1 string2 start1 end1 start2 end2))
202    
203     (defun string> (string1 string2 &key (start1 0) end1 (start2 0) end2)
204     "Given two strings, if the first string is lexicographically greater than
205     the second string, returns the longest common prefix (using char=)
206     of the two strings. Otherwise, returns ()."
207     (string>* string1 string2 start1 end1 start2 end2))
208    
209    
210     (defun string<= (string1 string2 &key (start1 0) end1 (start2 0) end2)
211     "Given two strings, if the first string is lexicographically less than
212     or equal to the second string, returns the longest common prefix
213     (using char=) of the two strings. Otherwise, returns ()."
214     (string<=* string1 string2 start1 end1 start2 end2))
215    
216     (defun string>= (string1 string2 &key (start1 0) end1 (start2 0) end2)
217     "Given two strings, if the first string is lexicographically greater
218     than or equal to the second string, returns the longest common prefix
219     (using char=) of the two strings. Otherwise, returns ()."
220     (string>=* string1 string2 start1 end1 start2 end2))
221    
222     (defun string= (string1 string2 &key (start1 0) end1 (start2 0) end2)
223     "Given two strings (string1 and string2), and optional integers start1,
224     start2, end1 and end2, compares characters in string1 to characters in
225     string2 (using char=)."
226     (string=* string1 string2 start1 end1 start2 end2))
227    
228     (defun string/= (string1 string2 &key (start1 0) end1 (start2 0) end2)
229     "Given two strings, if the first string is not lexicographically equal
230     to the second string, returns the longest common prefix (using char=)
231     of the two strings. Otherwise, returns ()."
232     (string/=* string1 string2 start1 end1 start2 end2))
233    
234    
235     (eval-when (compile eval)
236    
237     ;;; STRING-NOT-EQUAL-LOOP is used to generate character comparison loops for
238     ;;; STRING-EQUAL and STRING-NOT-EQUAL.
239     (defmacro string-not-equal-loop (end end-value
240     &optional (abort-value nil abortp))
241     (declare (fixnum end))
242     (let ((end-test (if (= end 1)
243     `(= index1 (the fixnum end1))
244     `(= index2 (the fixnum end2)))))
245     `(do ((index1 start1 (1+ index1))
246     (index2 start2 (1+ index2)))
247     (,(if abortp
248     end-test
249     `(or ,end-test
250     (not (char-equal (schar string1 index1)
251     (schar string2 index2)))))
252     ,end-value)
253     (declare (fixnum index1 index2))
254     ,@(if abortp
255     `((if (not (char-equal (schar string1 index1)
256     (schar string2 index2)))
257     (return ,abort-value)))))))
258    
259     ) ; eval-when
260    
261     (defun string-equal (string1 string2 &key (start1 0) end1 (start2 0) end2)
262     "Given two strings (string1 and string2), and optional integers start1,
263     start2, end1 and end2, compares characters in string1 to characters in
264     string2 (using char-equal)."
265     (declare (fixnum start1 start2))
266 ram 1.4 (with-two-strings string1 string2 start1 end1 offset1 start2 end2
267     (let ((slen1 (- (the fixnum end1) start1))
268     (slen2 (- (the fixnum end2) start2)))
269     (declare (fixnum slen1 slen2))
270     (if (or (minusp slen1) (minusp slen2))
271     ;;prevent endless looping later.
272     (error "Improper bounds for string comparison."))
273     (if (= slen1 slen2)
274     ;;return () immediately if lengths aren't equal.
275     (string-not-equal-loop 1 t nil)))))
276 ram 1.1
277     (defun string-not-equal (string1 string2 &key (start1 0) end1 (start2 0) end2)
278     "Given two strings, if the first string is not lexicographically equal
279     to the second string, returns the longest common prefix (using char-equal)
280     of the two strings. Otherwise, returns ()."
281 ram 1.4 (with-two-strings string1 string2 start1 end1 offset1 start2 end2
282     (let ((slen1 (- end1 start1))
283     (slen2 (- end2 start2)))
284     (declare (fixnum slen1 slen2))
285     (if (or (minusp slen1) (minusp slen2))
286     ;;prevent endless looping later.
287     (error "Improper bounds for string comparison."))
288     (cond ((or (minusp slen1) (or (minusp slen2)))
289     (error "Improper substring for comparison."))
290     ((= slen1 slen2)
291     (string-not-equal-loop 1 nil (- index1 offset1)))
292     ((< slen1 slen2)
293     (string-not-equal-loop 1 (- index1 offset1)))
294     (t
295     (string-not-equal-loop 2 (- index1 offset1)))))))
296 ram 1.1
297    
298    
299     (eval-when (compile eval)
300    
301     ;;; STRING-LESS-GREATER-EQUAL-TESTS returns a test on the lengths of string1
302     ;;; and string2 and a test on the current characters from string1 and string2
303     ;;; for the following macro.
304     (defun string-less-greater-equal-tests (lessp equalp)
305     (if lessp
306     (if equalp
307     ;; STRING-NOT-GREATERP
308     (values '<= `(not (char-greaterp char1 char2)))
309     ;; STRING-LESSP
310     (values '< `(char-lessp char1 char2)))
311     (if equalp
312     ;; STRING-NOT-LESSP
313     (values '>= `(not (char-lessp char1 char2)))
314     ;; STRING-GREATERP
315     (values '> `(char-greaterp char1 char2)))))
316    
317     (defmacro string-less-greater-equal (lessp equalp)
318     (multiple-value-bind (length-test character-test)
319     (string-less-greater-equal-tests lessp equalp)
320 ram 1.4 `(with-two-strings string1 string2 start1 end1 offset1 start2 end2
321     (let ((slen1 (- (the fixnum end1) start1))
322     (slen2 (- (the fixnum end2) start2)))
323     (declare (fixnum slen1 slen2))
324     (if (or (minusp slen1) (minusp slen2))
325     ;;prevent endless looping later.
326     (error "Improper bounds for string comparison."))
327     (do ((index1 start1 (1+ index1))
328     (index2 start2 (1+ index2))
329     (char1)
330     (char2))
331     ((or (= index1 (the fixnum end1)) (= index2 (the fixnum end2)))
332     (if (,length-test slen1 slen2) (- index1 offset1)))
333     (declare (fixnum index1 index2))
334     (setq char1 (schar string1 index1))
335     (setq char2 (schar string2 index2))
336     (if (not (char-equal char1 char2))
337     (if ,character-test
338     (return (- index1 offset1))
339     (return ()))))))))
340 ram 1.1
341     ) ; eval-when
342    
343     (defun string-lessp* (string1 string2 start1 end1 start2 end2)
344     (declare (fixnum start1 start2))
345     (string-less-greater-equal t nil))
346    
347     (defun string-greaterp* (string1 string2 start1 end1 start2 end2)
348     (declare (fixnum start1 start2))
349     (string-less-greater-equal nil nil))
350    
351     (defun string-not-lessp* (string1 string2 start1 end1 start2 end2)
352     (declare (fixnum start1 start2))
353     (string-less-greater-equal nil t))
354    
355     (defun string-not-greaterp* (string1 string2 start1 end1 start2 end2)
356     (declare (fixnum start1 start2))
357     (string-less-greater-equal t t))
358    
359     (defun string-lessp (string1 string2 &key (start1 0) end1 (start2 0) end2)
360     "Given two strings, if the first string is lexicographically less than
361     the second string, returns the longest common prefix (using char-equal)
362     of the two strings. Otherwise, returns ()."
363     (string-lessp* string1 string2 start1 end1 start2 end2))
364    
365     (defun string-greaterp (string1 string2 &key (start1 0) end1 (start2 0) end2)
366     "Given two strings, if the first string is lexicographically greater than
367     the second string, returns the longest common prefix (using char-equal)
368     of the two strings. Otherwise, returns ()."
369     (string-greaterp* string1 string2 start1 end1 start2 end2))
370    
371     (defun string-not-lessp (string1 string2 &key (start1 0) end1 (start2 0) end2)
372     "Given two strings, if the first string is lexicographically greater
373     than or equal to the second string, returns the longest common prefix
374     (using char-equal) of the two strings. Otherwise, returns ()."
375     (string-not-lessp* string1 string2 start1 end1 start2 end2))
376    
377     (defun string-not-greaterp (string1 string2 &key (start1 0) end1 (start2 0)
378     end2)
379     "Given two strings, if the first string is lexicographically less than
380     or equal to the second string, returns the longest common prefix
381     (using char-equal) of the two strings. Otherwise, returns ()."
382     (string-not-greaterp* string1 string2 start1 end1 start2 end2))
383    
384    
385 dtc 1.9 (defun make-string (count &key element-type ((:initial-element fill-char)))
386 ram 1.1 "Given a character count and an optional fill character, makes and returns
387     a new string Count long filled with the fill character."
388 emarsden 1.12 (declare (type fixnum count))
389     (assert (subtypep element-type 'character))
390 ram 1.1 (if fill-char
391     (do ((i 0 (1+ i))
392     (string (make-string count)))
393     ((= i count) string)
394     (declare (fixnum i))
395     (setf (schar string i) fill-char))
396     (make-string count)))
397    
398     (defun string-upcase (string &key (start 0) end)
399     "Given a string, returns a new string that is a copy of it with
400     all lower case alphabetic characters converted to uppercase."
401     (declare (fixnum start))
402 ram 1.5 (let* ((string (if (stringp string) string (string string)))
403     (slen (length string)))
404 ram 1.4 (declare (fixnum slen))
405 ram 1.1 (with-one-string string start end offset
406     (let ((offset-slen (+ slen offset))
407     (newstring (make-string slen)))
408     (declare (fixnum offset-slen))
409     (do ((index offset (1+ index))
410     (new-index 0 (1+ new-index)))
411     ((= index start))
412     (declare (fixnum index new-index))
413     (setf (schar newstring new-index) (schar string index)))
414     (do ((index start (1+ index))
415     (new-index (- start offset) (1+ new-index)))
416     ((= index (the fixnum end)))
417     (declare (fixnum index new-index))
418     (setf (schar newstring new-index)
419     (char-upcase (schar string index))))
420     (do ((index end (1+ index))
421     (new-index (- (the fixnum end) offset) (1+ new-index)))
422     ((= index offset-slen))
423     (declare (fixnum index new-index))
424     (setf (schar newstring new-index) (schar string index)))
425     newstring))))
426    
427     (defun string-downcase (string &key (start 0) end)
428     "Given a string, returns a new string that is a copy of it with
429     all upper case alphabetic characters converted to lowercase."
430     (declare (fixnum start))
431 ram 1.5 (let* ((string (if (stringp string) string (string string)))
432     (slen (length string)))
433 ram 1.4 (declare (fixnum slen))
434 ram 1.1 (with-one-string string start end offset
435     (let ((offset-slen (+ slen offset))
436     (newstring (make-string slen)))
437     (declare (fixnum offset-slen))
438     (do ((index offset (1+ index))
439     (new-index 0 (1+ new-index)))
440     ((= index start))
441     (declare (fixnum index new-index))
442     (setf (schar newstring new-index) (schar string index)))
443     (do ((index start (1+ index))
444     (new-index (- start offset) (1+ new-index)))
445     ((= index (the fixnum end)))
446     (declare (fixnum index new-index))
447     (setf (schar newstring new-index)
448     (char-downcase (schar string index))))
449     (do ((index end (1+ index))
450     (new-index (- (the fixnum end) offset) (1+ new-index)))
451     ((= index offset-slen))
452     (declare (fixnum index new-index))
453     (setf (schar newstring new-index) (schar string index)))
454     newstring))))
455    
456     (defun string-capitalize (string &key (start 0) end)
457     "Given a string, returns a copy of the string with the first
458     character of each ``word'' converted to upper-case, and remaining
459     chars in the word converted to lower case. A ``word'' is defined
460     to be a string of case-modifiable characters delimited by
461     non-case-modifiable chars."
462     (declare (fixnum start))
463 ram 1.5 (let* ((string (if (stringp string) string (string string)))
464     (slen (length string)))
465 ram 1.4 (declare (fixnum slen))
466 ram 1.1 (with-one-string string start end offset
467     (let ((offset-slen (+ slen offset))
468     (newstring (make-string slen)))
469     (declare (fixnum offset-slen))
470     (do ((index offset (1+ index))
471     (new-index 0 (1+ new-index)))
472     ((= index start))
473     (declare (fixnum index new-index))
474     (setf (schar newstring new-index) (schar string index)))
475     (do ((index start (1+ index))
476     (new-index (- start offset) (1+ new-index))
477     (newword t)
478     (char ()))
479     ((= index (the fixnum end)))
480     (declare (fixnum index new-index))
481     (setq char (schar string index))
482     (cond ((not (alphanumericp char))
483     (setq newword t))
484     (newword
485     ;;char is first case-modifiable after non-case-modifiable
486     (setq char (char-upcase char))
487     (setq newword ()))
488     ;;char is case-modifiable, but not first
489     (t (setq char (char-downcase char))))
490     (setf (schar newstring new-index) char))
491     (do ((index end (1+ index))
492     (new-index (- (the fixnum end) offset) (1+ new-index)))
493     ((= index offset-slen))
494     (declare (fixnum index new-index))
495     (setf (schar newstring new-index) (schar string index)))
496     newstring))))
497    
498     (defun nstring-upcase (string &key (start 0) end)
499     "Given a string, returns that string with all lower case alphabetic
500     characters converted to uppercase."
501     (declare (fixnum start))
502 ram 1.4 (let ((save-header string))
503 ram 1.1 (with-one-string string start end offset
504     (do ((index start (1+ index)))
505     ((= index (the fixnum end)))
506     (declare (fixnum index))
507     (setf (schar string index) (char-upcase (schar string index)))))
508     save-header))
509    
510     (defun nstring-downcase (string &key (start 0) end)
511     "Given a string, returns that string with all upper case alphabetic
512     characters converted to lowercase."
513     (declare (fixnum start))
514 ram 1.4 (let ((save-header string))
515 ram 1.1 (with-one-string string start end offset
516     (do ((index start (1+ index)))
517     ((= index (the fixnum end)))
518     (declare (fixnum index))
519     (setf (schar string index) (char-downcase (schar string index)))))
520 wlott 1.6 save-header))
521 ram 1.1
522     (defun nstring-capitalize (string &key (start 0) end)
523     "Given a string, returns that string with the first
524     character of each ``word'' converted to upper-case, and remaining
525     chars in the word converted to lower case. A ``word'' is defined
526     to be a string of case-modifiable characters delimited by
527     non-case-modifiable chars."
528     (declare (fixnum start))
529 ram 1.4 (let ((save-header string))
530 ram 1.1 (with-one-string string start end offset
531     (do ((index start (1+ index))
532     (newword t)
533     (char ()))
534     ((= index (the fixnum end)))
535     (declare (fixnum index))
536     (setq char (schar string index))
537     (cond ((not (alphanumericp char))
538     (setq newword t))
539     (newword
540     ;;char is first case-modifiable after non-case-modifiable
541     (setf (schar string index) (char-upcase char))
542     (setq newword ()))
543     (t
544     (setf (schar string index) (char-downcase char))))))
545     save-header))
546    
547     (defun string-left-trim (char-bag string)
548     "Given a set of characters (a list or string) and a string, returns
549     a copy of the string with the characters in the set removed from the
550     left end."
551     (with-string string
552     (do ((index start (1+ index)))
553     ((or (= index (the fixnum end))
554     (not (find (schar string index) char-bag)))
555     (subseq (the simple-string string) index end))
556     (declare (fixnum index)))))
557    
558     (defun string-right-trim (char-bag string)
559     "Given a set of characters (a list or string) and a string, returns
560     a copy of the string with the characters in the set removed from the
561     right end."
562     (with-string string
563     (do ((index (1- (the fixnum end)) (1- index)))
564     ((or (< index start) (not (find (schar string index) char-bag)))
565     (subseq (the simple-string string) start (1+ index)))
566     (declare (fixnum index)))))
567    
568     (defun string-trim (char-bag string)
569     "Given a set of characters (a list or string) and a string, returns a
570     copy of the string with the characters in the set removed from both
571     ends."
572     (with-string string
573     (let* ((left-end (do ((index start (1+ index)))
574     ((or (= index (the fixnum end))
575     (not (find (schar string index) char-bag)))
576     index)
577     (declare (fixnum index))))
578     (right-end (do ((index (1- (the fixnum end)) (1- index)))
579     ((or (< index left-end)
580     (not (find (schar string index) char-bag)))
581     (1+ index))
582     (declare (fixnum index)))))
583     (subseq (the simple-string string) left-end right-end))))

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