lisp/emacs-lisp/seq.el

   1 ;;; seq.el --- Sequence manipulation functions  -*- lexical-binding: t -*-
   2
   3 ;; Copyright (C) 2014-2016 Free Software Foundation, Inc.
   4
   5 ;; Author: Nicolas Petton <nicolas@petton.fr>
   6 ;; Keywords: sequences
   7 ;; Version: 2.19
   8 ;; Package: seq
   9
  10 ;; Maintainer: emacs-devel@gnu.org
  11
  12 ;; This file is part of GNU Emacs.
  13
  14 ;; GNU Emacs is free software: you can redistribute it and/or modify
  15 ;; it under the terms of the GNU General Public License as published by
  16 ;; the Free Software Foundation, either version 3 of the License, or
  17 ;; (at your option) any later version.
  18
  19 ;; GNU Emacs is distributed in the hope that it will be useful,
  20 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  21 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22 ;; GNU General Public License for more details.
  23
  24 ;; You should have received a copy of the GNU General Public License
  25 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  26
  27 ;;; Commentary:
  28
  29 ;; Sequence-manipulation functions that complement basic functions
  30 ;; provided by subr.el.
  31 ;;
  32 ;; All functions are prefixed with "seq-".
  33 ;;
  34 ;; All provided functions work on lists, strings and vectors.
  35 ;;
  36 ;; Functions taking a predicate or iterating over a sequence using a
  37 ;; function as argument take the function as their first argument and
  38 ;; the sequence as their second argument.  All other functions take
  39 ;; the sequence as their first argument.
  40 ;;
  41 ;; While seq.el version 1.8 is in GNU ELPA for convenience, seq.el
  42 ;; version 2.0 requires Emacs>=25.1.
  43 ;;
  44 ;; seq.el can be extended to support new type of sequences.  Here are
  45 ;; the generic functions that must be implemented by new seq types:
  46 ;; - `seq-elt'
  47 ;; - `seq-length'
  48 ;; - `seq-do'
  49 ;; - `seqp'
  50 ;; - `seq-subseq'
  51 ;; - `seq-into-sequence'
  52 ;; - `seq-copy'
  53 ;; - `seq-into'
  54 ;;
  55 ;; All functions are tested in test/automated/seq-tests.el
  56
  57 ;;; Code:
  58
  59 (eval-when-compile (require 'cl-generic))
  60 (require 'cl-lib) ;; for cl-subseq
  61
  62 (defmacro seq-doseq (spec &rest body)
  63   "Loop over a sequence.
  64 Evaluate BODY with VAR bound to each element of SEQUENCE, in turn.
  65
  66 Similar to `dolist' but can be applied to lists, strings, and vectors.
  67
  68 \(fn (VAR SEQUENCE) BODY...)"
  69   (declare (indent 1) (debug ((symbolp form &optional form) body)))
  70   `(seq-do (lambda (,(car spec))
  71              ,@body)
  72            ,(cadr spec)))
  73
  74 (pcase-defmacro seq (&rest patterns)
  75   "Build a `pcase' pattern that matches elements of SEQUENCE.
  76
  77 The `pcase' pattern will match each element of PATTERNS against the
  78 corresponding element of SEQUENCE.
  79
  80 Extra elements of the sequence are ignored if fewer PATTERNS are
  81 given, and the match does not fail."
  82   `(and (pred seqp)
  83         ,@(seq--make-pcase-bindings patterns)))
  84
  85 (defmacro seq-let (args sequence &rest body)
  86   "Bind the variables in ARGS to the elements of SEQUENCE, then evaluate BODY.
  87
  88 ARGS can also include the `&rest' marker followed by a variable
  89 name to be bound to the rest of SEQUENCE."
  90   (declare (indent 2) (debug (sexp form body)))
  91   `(pcase-let ((,(seq--make-pcase-patterns args) ,sequence))
  92      ,@body))
  93 \f
  94
  95 ;;; Basic seq functions that have to be implemented by new sequence types
  96 (cl-defgeneric seq-elt (sequence n)
  97   "Return Nth element of SEQUENCE."
  98   (elt sequence n))
  99
 100 ;; Default gv setters for `seq-elt'.
 101 ;; It can be a good idea for new sequence implementations to provide a
 102 ;; "gv-setter" for `seq-elt'.
 103 (cl-defmethod (setf seq-elt) (store (sequence array) n)
 104   (aset sequence n store))
 105
 106 (cl-defmethod (setf seq-elt) (store (sequence cons) n)
 107   (setcar (nthcdr n sequence) store))
 108
 109 (cl-defgeneric seq-length (sequence)
 110   "Return the number of elements of SEQUENCE."
 111   (length sequence))
 112
 113 (cl-defgeneric seq-do (function sequence)
 114   "Apply FUNCTION to each element of SEQUENCE, presumably for side effects.
 115 Return SEQUENCE."
 116   (mapc function sequence))
 117
 118 (defalias 'seq-each #'seq-do)
 119
 120 (defun seq-do-indexed (function sequence)
 121   "Apply FUNCTION to each element of SEQUENCE and return nil.
 122 Unlike `seq-map', FUNCTION takes two arguments: the element of
 123 the sequence, and its index within the sequence."
 124   (let ((index 0))
 125     (seq-do (lambda (elt)
 126                (funcall function elt index)
 127                (setq index (1+ index)))
 128              sequence)))
 129
 130 (cl-defgeneric seqp (sequence)
 131   "Return non-nil if SEQUENCE is a sequence, nil otherwise."
 132   (sequencep sequence))
 133
 134 (cl-defgeneric seq-copy (sequence)
 135   "Return a shallow copy of SEQUENCE."
 136   (copy-sequence sequence))
 137
 138 (cl-defgeneric seq-subseq (sequence start &optional end)
 139   "Return the sequence of elements of SEQUENCE from START to END.
 140 END is exclusive.
 141
 142 If END is omitted, it defaults to the length of the sequence.  If
 143 START or END is negative, it counts from the end.  Signal an
 144 error if START or END are outside of the sequence (i.e too large
 145 if positive or too small if negative)."
 146   (cl-subseq sequence start end))
 147
 148 \f
 149 (cl-defgeneric seq-map (function sequence)
 150   "Return the result of applying FUNCTION to each element of SEQUENCE."
 151   (let (result)
 152     (seq-do (lambda (elt)
 153               (push (funcall function elt) result))
 154             sequence)
 155     (nreverse result)))
 156
 157 (defun seq-map-indexed (function sequence)
 158   "Return the result of applying FUNCTION to each element of SEQUENCE.
 159 Unlike `seq-map', FUNCTION takes two arguments: the element of
 160 the sequence, and its index within the sequence."
 161   (let ((index 0))
 162     (seq-map (lambda (elt)
 163                (prog1
 164                    (funcall function elt index)
 165                  (setq index (1+ index))))
 166              sequence)))
 167
 168
 169 ;; faster implementation for sequences (sequencep)
 170 (cl-defmethod seq-map (function (sequence sequence))
 171   (mapcar function sequence))
 172
 173 (cl-defgeneric seq-mapn (function sequence &rest sequences)
 174   "Like `seq-map' but FUNCTION is mapped over all SEQUENCES.
 175 The arity of FUNCTION must match the number of SEQUENCES, and the
 176 mapping stops on the shortest sequence.
 177 Return a list of the results.
 178
 179 \(fn FUNCTION SEQUENCES...)"
 180   (let ((result nil)
 181         (sequences (seq-map (lambda (s) (seq-into s 'list))
 182                             (cons sequence sequences))))
 183     (while (not (memq nil sequences))
 184       (push (apply function (seq-map #'car sequences)) result)
 185       (setq sequences (seq-map #'cdr sequences)))
 186     (nreverse result)))
 187
 188 (cl-defgeneric seq-drop (sequence n)
 189   "Remove the first N elements of SEQUENCE and return the result.
 190 The result is a sequence of the same type as SEQUENCE.
 191
 192 If N is a negative integer or zero, SEQUENCE is returned."
 193   (if (<= n 0)
 194       sequence
 195     (let ((length (seq-length sequence)))
 196       (seq-subseq sequence (min n length) length))))
 197
 198 (cl-defgeneric seq-take (sequence n)
 199   "Take the first N elements of SEQUENCE and return the result.
 200 The result is a sequence of the same type as SEQUENCE.
 201
 202 If N is a negative integer or zero, an empty sequence is
 203 returned."
 204   (seq-subseq sequence 0 (min (max n 0) (seq-length sequence))))
 205
 206 (cl-defgeneric seq-drop-while (pred sequence)
 207   "Remove the successive elements of SEQUENCE for which PRED returns non-nil.
 208 PRED is a function of one argument.  The result is a sequence of
 209 the same type as SEQUENCE."
 210   (seq-drop sequence (seq--count-successive pred sequence)))
 211
 212 (cl-defgeneric seq-take-while (pred sequence)
 213   "Take the successive elements of SEQUENCE for which PRED returns non-nil.
 214 PRED is a function of one argument.  The result is a sequence of
 215 the same type as SEQUENCE."
 216   (seq-take sequence (seq--count-successive pred sequence)))
 217
 218 (cl-defgeneric seq-empty-p (sequence)
 219   "Return non-nil if the SEQUENCE is empty, nil otherwise."
 220   (= 0 (seq-length sequence)))
 221
 222 (cl-defgeneric seq-sort (pred sequence)
 223   "Sort SEQUENCE using PRED as comparison function.
 224 The result is a sequence of the same type as SEQUENCE."
 225   (let ((result (seq-sort pred (append sequence nil))))
 226     (seq-into result (type-of sequence))))
 227
 228 (cl-defmethod seq-sort (pred (list list))
 229   (sort (seq-copy list) pred))
 230
 231 (defun seq-sort-by (function pred sequence)
 232   "Sort SEQUENCE using PRED as a comparison function.
 233 Elements of SEQUENCE are transformed by FUNCTION before being
 234 sorted.  FUNCTION must be a function of one argument."
 235   (seq-sort (lambda (a b)
 236               (funcall pred
 237                        (funcall function a)
 238                        (funcall function b)))
 239             sequence))
 240
 241 (cl-defgeneric seq-reverse (sequence)
 242   "Return a sequence with elements of SEQUENCE in reverse order."
 243   (let ((result '()))
 244     (seq-map (lambda (elt)
 245                (push elt result))
 246              sequence)
 247     (seq-into result (type-of sequence))))
 248
 249 ;; faster implementation for sequences (sequencep)
 250 (cl-defmethod seq-reverse ((sequence sequence))
 251   (reverse sequence))
 252
 253 (cl-defgeneric seq-concatenate (type &rest sequences)
 254   "Concatenate SEQUENCES into a single sequence of type TYPE.
 255 TYPE must be one of following symbols: vector, string or list.
 256
 257 \n(fn TYPE SEQUENCE...)"
 258   (apply #'cl-concatenate type (seq-map #'seq-into-sequence sequences)))
 259
 260 (cl-defgeneric seq-into-sequence (sequence)
 261   "Convert SEQUENCE into a sequence.
 262
 263 The default implementation is to signal an error if SEQUENCE is not a
 264 sequence, specific functions should be implemented for new types
 265 of sequence."
 266   (unless (sequencep sequence)
 267     (error "Cannot convert %S into a sequence" sequence))
 268   sequence)
 269
 270 (cl-defgeneric seq-into (sequence type)
 271   "Concatenate the elements of SEQUENCE into a sequence of type TYPE.
 272 TYPE can be one of the following symbols: vector, string or
 273 list."
 274   (pcase type
 275     (`vector (vconcat sequence))
 276     (`string (concat sequence))
 277     (`list (append sequence nil))
 278     (_ (error "Not a sequence type name: %S" type))))
 279
 280 (cl-defgeneric seq-filter (pred sequence)
 281   "Return a list of all the elements for which (PRED element) is non-nil in SEQUENCE."
 282   (let ((exclude (make-symbol "exclude")))
 283     (delq exclude (seq-map (lambda (elt)
 284                              (if (funcall pred elt)
 285                                  elt
 286                                exclude))
 287                            sequence))))
 288
 289 (cl-defgeneric seq-remove (pred sequence)
 290   "Return a list of all the elements for which (PRED element) is nil in SEQUENCE."
 291   (seq-filter (lambda (elt) (not (funcall pred elt)))
 292               sequence))
 293
 294 (cl-defgeneric seq-reduce (function sequence initial-value)
 295   "Reduce the function FUNCTION across SEQUENCE, starting with INITIAL-VALUE.
 296
 297 Return the result of calling FUNCTION with INITIAL-VALUE and the
 298 first element of SEQUENCE, then calling FUNCTION with that result and
 299 the second element of SEQUENCE, then with that result and the third
 300 element of SEQUENCE, etc.
 301
 302 If SEQUENCE is empty, return INITIAL-VALUE and FUNCTION is not called."
 303   (if (seq-empty-p sequence)
 304       initial-value
 305     (let ((acc initial-value))
 306       (seq-doseq (elt sequence)
 307         (setq acc (funcall function acc elt)))
 308       acc)))
 309
 310 (cl-defgeneric seq-every-p (pred sequence)
 311   "Return non-nil if (PRED element) is non-nil for all elements of SEQUENCE."
 312   (catch 'seq--break
 313     (seq-doseq (elt sequence)
 314       (or (funcall pred elt)
 315           (throw 'seq--break nil)))
 316     t))
 317
 318 (cl-defgeneric seq-some (pred sequence)
 319   "Return the first value for which if (PRED element) is non-nil for in SEQUENCE."
 320   (catch 'seq--break
 321     (seq-doseq (elt sequence)
 322       (let ((result (funcall pred elt)))
 323         (when result
 324           (throw 'seq--break result))))
 325     nil))
 326
 327 (cl-defgeneric seq-find (pred sequence &optional default)
 328   "Return the first element for which (PRED element) is non-nil in SEQUENCE.
 329 If no element is found, return DEFAULT.
 330
 331 Note that `seq-find' has an ambiguity if the found element is
 332 identical to DEFAULT, as it cannot be known if an element was
 333 found or not."
 334   (catch 'seq--break
 335     (seq-doseq (elt sequence)
 336       (when (funcall pred elt)
 337         (throw 'seq--break elt)))
 338     default))
 339
 340 (cl-defgeneric seq-count (pred sequence)
 341   "Return the number of elements for which (PRED element) is non-nil in SEQUENCE."
 342   (let ((count 0))
 343     (seq-doseq (elt sequence)
 344       (when (funcall pred elt)
 345         (setq count (+ 1 count))))
 346     count))
 347
 348 (cl-defgeneric seq-contains (sequence elt &optional testfn)
 349   "Return the first element in SEQUENCE that is equal to ELT.
 350 Equality is defined by TESTFN if non-nil or by `equal' if nil."
 351   (seq-some (lambda (e)
 352               (when (funcall (or testfn #'equal) elt e)
 353                 e))
 354             sequence))
 355
 356 (cl-defgeneric seq-position (sequence elt &optional testfn)
 357   "Return the index of the first element in SEQUENCE that is equal to ELT.
 358 Equality is defined by TESTFN if non-nil or by `equal' if nil."
 359   (let ((index 0))
 360     (catch 'seq--break
 361       (seq-doseq (e sequence)
 362         (when (funcall (or testfn #'equal) e elt)
 363           (throw 'seq--break index))
 364         (setq index (1+ index)))
 365       nil)))
 366
 367 (cl-defgeneric seq-uniq (sequence &optional testfn)
 368   "Return a list of the elements of SEQUENCE with duplicates removed.
 369 TESTFN is used to compare elements, or `equal' if TESTFN is nil."
 370   (let ((result '()))
 371     (seq-doseq (elt sequence)
 372       (unless (seq-contains result elt testfn)
 373         (setq result (cons elt result))))
 374     (nreverse result)))
 375
 376 (cl-defgeneric seq-mapcat (function sequence &optional type)
 377   "Concatenate the result of applying FUNCTION to each element of SEQUENCE.
 378 The result is a sequence of type TYPE, or a list if TYPE is nil."
 379   (apply #'seq-concatenate (or type 'list)
 380          (seq-map function sequence)))
 381
 382 (cl-defgeneric seq-partition (sequence n)
 383   "Return a list of the elements of SEQUENCE grouped into sub-sequences of length N.
 384 The last sequence may contain less than N elements.  If N is a
 385 negative integer or 0, nil is returned."
 386   (unless (< n 1)
 387     (let ((result '()))
 388       (while (not (seq-empty-p sequence))
 389         (push (seq-take sequence n) result)
 390         (setq sequence (seq-drop sequence n)))
 391       (nreverse result))))
 392
 393 (cl-defgeneric seq-intersection (sequence1 sequence2 &optional testfn)
 394   "Return a list of the elements that appear in both SEQUENCE1 and SEQUENCE2.
 395 Equality is defined by TESTFN if non-nil or by `equal' if nil."
 396   (seq-reduce (lambda (acc elt)
 397                 (if (seq-contains sequence2 elt testfn)
 398                     (cons elt acc)
 399                   acc))
 400               (seq-reverse sequence1)
 401               '()))
 402
 403 (cl-defgeneric seq-difference (sequence1 sequence2 &optional testfn)
 404   "Return a list of the elements that appear in SEQUENCE1 but not in SEQUENCE2.
 405 Equality is defined by TESTFN if non-nil or by `equal' if nil."
 406   (seq-reduce (lambda (acc elt)
 407                 (if (not (seq-contains sequence2 elt testfn))
 408                     (cons elt acc)
 409                   acc))
 410               (seq-reverse sequence1)
 411               '()))
 412
 413 (cl-defgeneric seq-group-by (function sequence)
 414   "Apply FUNCTION to each element of SEQUENCE.
 415 Separate the elements of SEQUENCE into an alist using the results as
 416 keys.  Keys are compared using `equal'."
 417   (seq-reduce
 418    (lambda (acc elt)
 419      (let* ((key (funcall function elt))
 420             (cell (assoc key acc)))
 421        (if cell
 422            (setcdr cell (push elt (cdr cell)))
 423          (push (list key elt) acc))
 424        acc))
 425    (seq-reverse sequence)
 426    nil))
 427
 428 (cl-defgeneric seq-min (sequence)
 429   "Return the smallest element of SEQUENCE.
 430 SEQUENCE must be a sequence of numbers or markers."
 431   (apply #'min (seq-into sequence 'list)))
 432
 433 (cl-defgeneric seq-max (sequence)
 434   "Return the largest element of SEQUENCE.
 435 SEQUENCE must be a sequence of numbers or markers."
 436   (apply #'max (seq-into sequence 'list)))
 437
 438 (defun seq--count-successive (pred sequence)
 439   "Return the number of successive elements for which (PRED element) is non-nil in SEQUENCE."
 440   (let ((n 0)
 441         (len (seq-length sequence)))
 442     (while (and (< n len)
 443                 (funcall pred (seq-elt sequence n)))
 444       (setq n (+ 1 n)))
 445     n))
 446
 447 (defun seq--make-pcase-bindings (args)
 448   "Return a list of bindings of the variables in ARGS to the elements of a sequence."
 449   (let ((bindings '())
 450         (index 0)
 451         (rest-marker nil))
 452     (seq-doseq (name args)
 453       (unless rest-marker
 454         (pcase name
 455           (`&rest
 456            (progn (push `(app (pcase--flip seq-drop ,index)
 457                               ,(seq--elt-safe args (1+ index)))
 458                         bindings)
 459                   (setq rest-marker t)))
 460           (_
 461            (push `(app (pcase--flip seq--elt-safe ,index) ,name) bindings))))
 462       (setq index (1+ index)))
 463     bindings))
 464
 465 (defun seq--make-pcase-patterns (args)
 466   "Return a list of `(seq ...)' pcase patterns from the argument list ARGS."
 467   (cons 'seq
 468         (seq-map (lambda (elt)
 469                    (if (seqp elt)
 470                        (seq--make-pcase-patterns elt)
 471                      elt))
 472                  args)))
 473
 474 ;; TODO: make public?
 475 (defun seq--elt-safe (sequence n)
 476   "Return element of SEQUENCE at the index N.
 477 If no element is found, return nil."
 478   (ignore-errors (seq-elt sequence n)))
 479
 480 (cl-defgeneric seq-random-elt (sequence)
 481   "Return a random element from SEQUENCE.
 482 Signal an error if SEQUENCE is empty."
 483   (if (seq-empty-p sequence)
 484       (error "Sequence cannot be empty")
 485     (seq-elt sequence (random (seq-length sequence)))))
 486 \f
 487
 488 ;;; Optimized implementations for lists
 489
 490 (cl-defmethod seq-drop ((list list) n)
 491   "Optimized implementation of `seq-drop' for lists."
 492   (nthcdr n list))
 493
 494 (cl-defmethod seq-take ((list list) n)
 495   "Optimized implementation of `seq-take' for lists."
 496   (let ((result '()))
 497     (while (and list (> n 0))
 498       (setq n (1- n))
 499       (push (pop list) result))
 500     (nreverse result)))
 501
 502 (cl-defmethod seq-drop-while (pred (list list))
 503   "Optimized implementation of `seq-drop-while' for lists."
 504   (while (and list (funcall pred (car list)))
 505     (setq list (cdr list)))
 506   list)
 507
 508 (cl-defmethod seq-empty-p ((list list))
 509   "Optimized implementation of `seq-empty-p' for lists."
 510   (null list))
 511 \f
 512
 513 (defun seq--activate-font-lock-keywords ()
 514   "Activate font-lock keywords for some symbols defined in seq."
 515   (font-lock-add-keywords 'emacs-lisp-mode
 516                           '("\\<seq-doseq\\>" "\\<seq-let\\>")))
 517
 518 (unless (fboundp 'elisp--font-lock-flush-elisp-buffers)
 519   ;; In Emacs≥25, (via elisp--font-lock-flush-elisp-buffers and a few others)
 520   ;; we automatically highlight macros.
 521   (add-hook 'emacs-lisp-mode-hook #'seq--activate-font-lock-keywords))
 522
 523 (provide 'seq)
 524 ;;; seq.el ends here