Replace DELETE-FROM-PLIST implementation, shorter and faster.
[projects/alexandria/alexandria.git] / lists.lisp
... / ...
1(in-package :alexandria)
3(declaim (inline safe-endp))
4(defun safe-endp (x)
5 (declare (optimize safety))
6 (endp x))
8(defun alist-plist (alist)
9 "Returns a property list containing the same keys and values as the
10association list ALIST in the same order."
11 (let (plist)
12 (dolist (pair alist)
13 (push (car pair) plist)
14 (push (cdr pair) plist))
15 (nreverse plist)))
17(defun plist-alist (plist)
18 "Returns an association list containing the same keys and values as the
19property list PLIST in the same order."
20 (let (alist)
21 (do ((tail plist (cddr tail)))
22 ((safe-endp tail) (nreverse alist))
23 (push (cons (car tail) (cadr tail)) alist))))
25(declaim (inline racons))
26(defun racons (key value ralist)
27 (acons value key ralist))
30 ((define-alist-get (name get-entry get-value-from-entry add doc)
31 `(progn
32 (declaim (inline ,name))
33 (defun ,name (alist key &key (test 'eql))
34 ,doc
35 (let ((entry (,get-entry key alist :test test)))
36 (values (,get-value-from-entry entry) entry)))
37 (define-setf-expander ,name (place key &key (test ''eql)
38 &environment env)
39 (multiple-value-bind
40 (temporary-variables initforms newvals setter getter)
41 (get-setf-expansion place env)
42 (when (cdr newvals)
43 (error "~A cannot store multiple values in one place" ',name))
44 (with-unique-names (new-value key-val test-val alist entry)
45 (values
46 (append temporary-variables
47 (list alist
48 key-val
49 test-val
50 entry))
51 (append initforms
52 (list getter
53 key
54 test
55 `(,',get-entry ,key-val ,alist :test ,test-val)))
56 `(,new-value)
57 `(cond
58 (,entry
59 (setf (,',get-value-from-entry ,entry) ,new-value))
60 (t
61 (let ,newvals
62 (setf ,(first newvals) (,',add ,key ,new-value ,alist))
63 ,setter
64 ,new-value)))
65 `(,',get-value-from-entry ,entry))))))))
66 (define-alist-get assoc-value assoc cdr acons
67"ASSOC-VALUE is an alist accessor very much like ASSOC, but it can
68be used with SETF.")
69 (define-alist-get rassoc-value rassoc car racons
70"RASSOC-VALUE is an alist accessor very much like RASSOC, but it can
71be used with SETF."))
73(defun malformed-plist (plist)
74 (error "Malformed plist: ~S" plist))
76(defmacro doplist ((key val plist &optional values) &body body)
77 "Iterates over elements of PLIST. BODY can be preceded by
78declarations, and is like a TAGBODY. RETURN may be used to terminate
79the iteration early. If RETURN is not used, returns VALUES."
80 (multiple-value-bind (forms declarations) (parse-body body)
81 (with-gensyms (tail loop results)
82 `(block nil
83 (flet ((,results ()
84 (let (,key ,val)
85 (declare (ignorable ,key ,val))
86 (return ,values))))
87 (let* ((,tail ,plist)
88 (,key (if ,tail
89 (pop ,tail)
90 (,results)))
91 (,val (if ,tail
92 (pop ,tail)
93 (malformed-plist ',plist))))
94 (declare (ignorable ,key ,val))
95 ,@declarations
96 (tagbody
97 ,loop
98 ,@forms
99 (setf ,key (if ,tail
100 (pop ,tail)
101 (,results))
102 ,val (if ,tail
103 (pop ,tail)
104 (malformed-plist ',plist)))
105 (go ,loop))))))))
107(define-modify-macro appendf (&rest lists) append
108 "Modify-macro for APPEND. Appends LISTS to the place designated by the first
111(define-modify-macro nconcf (&rest lists) nconc
112 "Modify-macro for NCONC. Concatenates LISTS to place designated by the first
115(define-modify-macro unionf (list &rest args) union
116 "Modify-macro for UNION. Saves the union of LIST and the contents of the
117place designated by the first argument to the designated place.")
119(define-modify-macro nunionf (list &rest args) nunion
120 "Modify-macro for NUNION. Saves the union of LIST and the contents of the
121place designated by the first argument to the designated place. May modify
122either argument.")
124(define-modify-macro reversef () reverse
125 "Modify-macro for REVERSE. Copies and reverses the list stored in the given
126place and saves back the result into the place.")
128(define-modify-macro nreversef () nreverse
129 "Modify-macro for NREVERSE. Reverses the list stored in the given place by
130destructively modifying it and saves back the result into the place.")
132(defun circular-list (&rest elements)
133 "Creates a circular list of ELEMENTS."
134 (let ((cycle (copy-list elements)))
135 (nconc cycle cycle)))
137(defun circular-list-p (object)
138 "Returns true if OBJECT is a circular list, NIL otherwise."
139 (and (listp object)
140 (do ((fast object (cddr fast))
141 (slow (cons (car object) (cdr object)) (cdr slow)))
142 (nil)
143 (unless (and (consp fast) (listp (cdr fast)))
144 (return nil))
145 (when (eq fast slow)
146 (return t)))))
148(defun circular-tree-p (object)
149 "Returns true if OBJECT is a circular tree, NIL otherwise."
150 (labels ((circularp (object seen)
151 (and (consp object)
152 (do ((fast (cons (car object) (cdr object)) (cddr fast))
153 (slow object (cdr slow)))
154 (nil)
155 (when (or (eq fast slow) (member slow seen))
156 (return-from circular-tree-p t))
157 (when (or (not (consp fast)) (not (consp (cdr slow))))
158 (return
159 (do ((tail object (cdr tail)))
160 ((not (consp tail))
161 nil)
162 (let ((elt (car tail)))
163 (circularp elt (cons object seen))))))))))
164 (circularp object nil)))
166(defun proper-list-p (object)
167 "Returns true if OBJECT is a proper list."
168 (cond ((not object)
169 t)
170 ((consp object)
171 (do ((fast object (cddr fast))
172 (slow (cons (car object) (cdr object)) (cdr slow)))
173 (nil)
174 (unless (and (listp fast) (consp (cdr fast)))
175 (return (and (listp fast) (not (cdr fast)))))
176 (when (eq fast slow)
177 (return nil))))
178 (t
179 nil)))
181(deftype proper-list ()
182 "Type designator for proper lists. Implemented as a SATISFIES type, hence
183not recommended for performance intensive use. Main usefullness as a type
184designator of the expected type in a TYPE-ERROR."
185 `(and list (satisfies proper-list-p)))
187(defun circular-list-error (list)
188 (error 'type-error
189 :datum list
190 :expected-type '(and list (not circular-list))))
192(macrolet ((def (name lambda-list doc step declare ret1 ret2)
193 (assert (member 'list lambda-list))
194 `(defun ,name ,lambda-list
195 ,doc
196 (do ((last list fast)
197 (fast list (cddr fast))
198 (slow (cons (car list) (cdr list)) (cdr slow))
199 ,@(when step (list step)))
200 (nil)
201 (declare (dynamic-extent slow) ,@(when declare (list declare))
202 (ignorable last))
203 (when (safe-endp fast)
204 (return ,ret1))
205 (when (safe-endp (cdr fast))
206 (return ,ret2))
207 (when (eq fast slow)
208 (circular-list-error list))))))
209 (def proper-list-length (list)
210 "Returns length of LIST, signalling an error if it is not a proper list."
211 (n 1 (+ n 2))
212 ;; KLUDGE: Most implementations don't actually support lists with bignum
213 ;; elements -- and this is WAY faster on most implementations then declaring
214 ;; N to be an UNSIGNED-BYTE.
215 (fixnum n)
216 (1- n)
217 n)
219 (def lastcar (list)
220 "Returns the last element of LIST. Signals a type-error if LIST is not a
221proper list."
222 nil
223 nil
224 (cadr last)
225 (car fast))
227 (def (setf lastcar) (object list)
228 "Sets the last element of LIST. Signals a type-error if LIST is not a proper
230 nil
231 nil
232 (setf (cadr last) object)
233 (setf (car fast) object)))
235(defun make-circular-list (length &key initial-element)
236 "Creates a circular list of LENGTH with the given INITIAL-ELEMENT."
237 (let ((cycle (make-list length :initial-element initial-element)))
238 (nconc cycle cycle)))
240(deftype circular-list ()
241 "Type designator for circular lists. Implemented as a SATISFIES type, so not
242recommended for performance intensive use. Main usefullness as the
243expected-type designator of a TYPE-ERROR."
244 `(satisfies circular-list-p))
246(defun ensure-car (thing)
247 "If THING is a CONS, its CAR is returned. Otherwise THING is returned."
248 (if (consp thing)
249 (car thing)
250 thing))
252(defun ensure-cons (cons)
253 "If CONS is a cons, it is returned. Otherwise returns a fresh cons with CONS
254 in the car, and NIL in the cdr."
255 (if (consp cons)
256 cons
257 (cons cons nil)))
259(defun ensure-list (list)
260 "If LIST is a list, it is returned. Otherwise returns the list designated by LIST."
261 (if (listp list)
262 list
263 (list list)))
265(defun remove-from-plist (plist &rest keys)
266 "Returns a propery-list with same keys and values as PLIST, except that keys
267in the list designated by KEYS and values corresponding to them are removed.
268The returned property-list may share structure with the PLIST, but PLIST is
269not destructively modified. Keys are compared using EQ."
270 (declare (optimize (speed 3)))
271 ;; FIXME: possible optimization: (remove-from-plist '(:x 0 :a 1 :b 2) :a)
272 ;; could return the tail without consing up a new list.
273 (loop for (key . rest) on plist by #'cddr
274 do (assert rest () "Expected a proper plist, got ~S" plist)
275 unless (member key keys :test #'eq)
276 collect key and collect (first rest)))
278(defun delete-from-plist (plist &rest keys)
279 "Just like REMOVE-FROM-PLIST, but this version may destructively modify the
280provided plist."
281 ;; FIXME: should not cons
282 (apply 'remove-from-plist plist keys))
284(define-modify-macro remove-from-plistf (&rest keys) remove-from-plist
285 "Modify macro for REMOVE-FROM-PLIST.")
286(define-modify-macro delete-from-plistf (&rest keys) delete-from-plist
287 "Modify macro for DELETE-FROM-PLIST.")
289(declaim (inline sans))
290(defun sans (plist &rest keys)
291 "Alias of REMOVE-FROM-PLIST for backward compatibility."
292 (apply #'remove-from-plist plist keys))
294(defun mappend (function &rest lists)
295 "Applies FUNCTION to respective element(s) of each LIST, appending all the
296all the result list to a single list. FUNCTION must return a list."
297 (loop for results in (apply #'mapcar function lists)
298 append results))
300(defun setp (object &key (test #'eql) (key #'identity))
301 "Returns true if OBJECT is a list that denotes a set, NIL otherwise. A list
302denotes a set if each element of the list is unique under KEY and TEST."
303 (and (listp object)
304 (let (seen)
305 (dolist (elt object t)
306 (let ((key (funcall key elt)))
307 (if (member key seen :test test)
308 (return nil)
309 (push key seen)))))))
311(defun set-equal (list1 list2 &key (test #'eql) (key nil keyp))
312 "Returns true if every element of LIST1 matches some element of LIST2 and
313every element of LIST2 matches some element of LIST1. Otherwise returns false."
314 (let ((keylist1 (if keyp (mapcar key list1) list1))
315 (keylist2 (if keyp (mapcar key list2) list2)))
316 (and (dolist (elt keylist1 t)
317 (or (member elt keylist2 :test test)
318 (return nil)))
319 (dolist (elt keylist2 t)
320 (or (member elt keylist1 :test test)
321 (return nil))))))
323(defun map-product (function list &rest more-lists)
324 "Returns a list containing the results of calling FUNCTION with one argument
325from LIST, and one from each of MORE-LISTS for each combination of arguments.
326In other words, returns the product of LIST and MORE-LISTS using FUNCTION.
330 (map-product 'list '(1 2) '(3 4) '(5 6))
331 => ((1 3 5) (1 3 6) (1 4 5) (1 4 6)
332 (2 3 5) (2 3 6) (2 4 5) (2 4 6))
334 (labels ((%map-product (f lists)
335 (let ((more (cdr lists))
336 (one (car lists)))
337 (if (not more)
338 (mapcar f one)
339 (mappend (lambda (x)
340 (%map-product (curry f x) more))
341 one)))))
342 (%map-product (ensure-function function) (cons list more-lists))))
344(defun flatten (tree)
345 "Traverses the tree in order, collecting non-null leaves into a list."
346 (let (list)
347 (labels ((traverse (subtree)
348 (when subtree
349 (if (consp subtree)
350 (progn
351 (traverse (car subtree))
352 (traverse (cdr subtree)))
353 (push subtree list)))))
354 (traverse tree))
355 (nreverse list)))