--- /dev/null
+;;; seq.el --- Sequence manipulation functions -*- lexical-binding: t -*-
+
+;; Copyright (C) 2014 Free Software Foundation, Inc.
+
+;; Author: Nicolas Petton <petton.nicolas@gmail.com>
+;; Keywords: sequences
+;; Version: 1.0
+;; Package: seq
+
+;; Maintainer: emacs-devel@gnu.org
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Sequence-manipulation functions that complement basic functions
+;; provided by subr.el.
+;;
+;; All functions are prefixed with "seq-".
+;;
+;; All provided functions work on lists, strings and vectors.
+;;
+;; Functions taking a predicate or a function iterating over the
+;; sequence as argument take the function as their first argument and
+;; the sequence as their second argument. All other functions take
+;; the sequence as their first argument.
+;;
+;; All functions are tested in test/automated/seq-tests.el
+
+;;; Code:
+
+(defmacro seq-doseq (spec &rest body)
+ "Loop over a sequence.
+Similar to `dolist' but can be applied lists, strings and vectors.
+
+Evaluate BODY with VAR bound to each element of SEQ, in turn.
+Then evaluate RESULT to get return value, default nil.
+
+\(fn (VAR SEQ [RESULT]) BODY...)"
+ (declare (indent 1) (debug ((symbolp form &optional form) body)))
+ (let ((is-list (make-symbol "is-list"))
+ (seq (make-symbol "seq"))
+ (index (make-symbol "index")))
+ `(let* ((,seq ,(cadr spec))
+ (,is-list (listp ,seq))
+ (,index (if ,is-list ,seq 0)))
+ (while (if ,is-list
+ (consp ,index)
+ (< ,index (seq-length ,seq)))
+ (let ((,(car spec) (if ,is-list
+ (car ,index)
+ (seq-elt ,seq ,index))))
+ ,@body
+ (setq ,index (if ,is-list
+ (cdr ,index)
+ (+ ,index 1)))))
+ ,@(if (cddr spec)
+ `((setq ,(car spec) nil) ,@(cddr spec))))))
+
+(defun seq-drop (seq n)
+ "Return a subsequence of SEQ without its first N elements.
+The result is a sequence of the same type as SEQ.
+
+If N is a negative integer or zero, SEQ is returned."
+ (if (<= n 0)
+ seq
+ (if (listp seq)
+ (seq--drop-list seq n)
+ (let ((length (seq-length seq)))
+ (seq-subseq seq (min n length) length)))))
+
+(defun seq-take (seq n)
+ "Return a subsequence of SEQ with its first N elements.
+The result is a sequence of the same type as SEQ.
+
+If N is a negative integer or zero, an empty sequence is
+returned."
+ (if (listp seq)
+ (seq--take-list seq n)
+ (seq-subseq seq 0 (min (max n 0) (seq-length seq)))))
+
+(defun seq-drop-while (pred seq)
+ "Return a sequence, from the first element for which (PRED element) is nil, of SEQ.
+The result is a sequence of the same type as SEQ."
+ (if (listp seq)
+ (seq--drop-while-list pred seq)
+ (seq-drop seq (seq--count-successive pred seq))))
+
+(defun seq-take-while (pred seq)
+ "Return a sequence of the successive elements for which (PRED element) is non-nil in SEQ.
+The result is a sequence of the same type as SEQ."
+ (if (listp seq)
+ (seq--take-while-list pred seq)
+ (seq-take seq (seq--count-successive pred seq))))
+
+(defun seq-filter (pred seq)
+ "Return a list of all the elements for which (PRED element) is non-nil in SEQ."
+ (let ((exclude (make-symbol "exclude")))
+ (delq exclude (seq-map (lambda (elt)
+ (if (funcall pred elt)
+ elt
+ exclude))
+ seq))))
+
+(defun seq-remove (pred seq)
+ "Return a list of all the elements for which (PRED element) is nil in SEQ."
+ (seq-filter (lambda (elt) (not (funcall pred elt)))
+ seq))
+
+(defun seq-reduce (function seq initial-value)
+ "Reduce the function FUNCTION across SEQ, starting with INITIAL-VALUE.
+
+Return the result of calling FUNCTION with INITIAL-VALUE and the
+first element of SEQ, then calling FUNCTION with that result and
+the second element of SEQ, then with that result and the third
+element of SEQ, etc.
+
+If SEQ is empty, return INITIAL-VALUE and FUNCTION is not called."
+ (if (seq-empty-p seq)
+ initial-value
+ (let ((acc initial-value))
+ (seq-doseq (elt seq)
+ (setq acc (funcall function acc elt)))
+ acc)))
+
+(defun seq-some-p (pred seq)
+ "Return any element for which (PRED element) is non-nil in SEQ, nil otherwise."
+ (catch 'seq--break
+ (seq-doseq (elt seq)
+ (when (funcall pred elt)
+ (throw 'seq--break elt)))
+ nil))
+
+(defun seq-every-p (pred seq)
+ "Return non-nil if (PRED element) is non-nil for all elements of the sequence SEQ."
+ (catch 'seq--break
+ (seq-doseq (elt seq)
+ (or (funcall pred elt)
+ (throw 'seq--break nil)))
+ t))
+
+(defun seq-count (pred seq)
+ "Return the number of elements for which (PRED element) returns non-nil in seq."
+ (let ((count 0))
+ (seq-doseq (elt seq)
+ (when (funcall pred elt)
+ (setq count (+ 1 count))))
+ count))
+
+(defun seq-empty-p (seq)
+ "Return non-nil if the sequence SEQ is empty, nil otherwise."
+ (if (listp seq)
+ (null seq)
+ (= 0 (seq-length seq))))
+
+(defun seq-sort (pred seq)
+ "Return a sorted sequence comparing using PRED the elements of SEQ.
+The result is a sequence of the same type as SEQ."
+ (if (listp seq)
+ (sort (seq-copy seq) pred)
+ (let ((result (seq-sort pred (append seq nil))))
+ (cond ((stringp seq) (concat result))
+ ((vectorp seq) (vconcat result))
+ (t (error "Unsupported sequence: %s" seq))))))
+
+(defun seq-contains-p (seq elt &optional testfn)
+ "Return the first element in SEQ that equals to ELT.
+Equality is defined by TESTFN if non-nil or by `equal' if nil."
+ (seq-some-p (lambda (e)
+ (funcall (or testfn #'equal) elt e))
+ seq))
+
+(defun seq-uniq (seq &optional testfn)
+ "Return a list of the elements of SEQ with duplicates removed.
+TESTFN is used to compare elements, or `equal' if TESTFN is nil."
+ (let ((result '()))
+ (seq-doseq (elt seq)
+ (unless (seq-contains-p result elt testfn)
+ (setq result (cons elt result))))
+ (nreverse result)))
+
+(defun seq-subseq (seq start &optional end)
+ "Return the subsequence of SEQ from START to END.
+If END is omitted, it defaults to the length of the sequence.
+If START or END is negative, it counts from the end."
+ (cond ((or (stringp seq) (vectorp seq)) (substring seq start end))
+ ((listp seq)
+ (let (len)
+ (and end (< end 0) (setq end (+ end (setq len (seq-length seq)))))
+ (if (< start 0) (setq start (+ start (or len (setq len (seq-length seq))))))
+ (if (> start 0) (setq seq (nthcdr start seq)))
+ (if end
+ (let ((res nil))
+ (while (>= (setq end (1- end)) start)
+ (push (pop seq) res))
+ (nreverse res))
+ (seq-copy seq))))
+ (t (error "Unsupported sequence: %s" seq))))
+
+(defun seq-concatenate (type &rest seqs)
+ "Concatenate, into a sequence of type TYPE, the sequences SEQS.
+TYPE must be one of following symbols: vector, string or list.
+
+\n(fn TYPE SEQUENCE...)"
+ (pcase type
+ (`vector (apply #'vconcat seqs))
+ (`string (apply #'concat seqs))
+ (`list (apply #'append (append seqs '(nil))))
+ (t (error "Not a sequence type name: %s" type))))
+
+(defun seq--drop-list (list n)
+ "Optimized version of `seq-drop' for lists."
+ (while (and list (> n 0))
+ (setq list (cdr list)
+ n (1- n)))
+ list)
+
+(defun seq--take-list (list n)
+ "Optimized version of `seq-take' for lists."
+ (let ((result '()))
+ (while (and list (> n 0))
+ (setq n (1- n))
+ (push (pop list) result))
+ (nreverse result)))
+
+(defun seq--drop-while-list (pred list)
+ "Optimized version of `seq-drop-while' for lists."
+ (while (and list (funcall pred (car list)))
+ (setq list (cdr list)))
+ list)
+
+(defun seq--take-while-list (pred list)
+ "Optimized version of `seq-take-while' for lists."
+ (let ((result '()))
+ (while (and list (funcall pred (car list)))
+ (push (pop list) result))
+ (nreverse result)))
+
+(defun seq--count-successive (pred seq)
+ "Return the number of successive elements for which (PRED element) is non-nil in SEQ."
+ (let ((n 0)
+ (len (seq-length seq)))
+ (while (and (< n len)
+ (funcall pred (seq-elt seq n)))
+ (setq n (+ 1 n)))
+ n))
+
+(defalias 'seq-copy #'copy-sequence)
+(defalias 'seq-elt #'elt)
+(defalias 'seq-reverse #'reverse)
+(defalias 'seq-length #'length)
+(defalias 'seq-do #'mapc)
+(defalias 'seq-each #'seq-do)
+(defalias 'seq-map #'mapcar)
+
+(provide 'seq)
+;;; seq.el ends here