;;; seq.el --- Sequence manipulation functions -*- lexical-binding: t -*-
-;; Copyright (C) 2014 Free Software Foundation, Inc.
+;; Copyright (C) 2014-2015 Free Software Foundation, Inc.
-;; Author: Nicolas Petton <petton.nicolas@gmail.com>
+;; Author: Nicolas Petton <nicolas@petton.fr>
;; Keywords: sequences
-;; Version: 1.0
+;; Version: 1.1
;; Package: seq
;; Maintainer: emacs-devel@gnu.org
(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.
+ "Return a sequence from the first element for which (PRED element) is nil in 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.
+ "Return 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)
t))
(defun seq-count (pred seq)
- "Return the number of elements for which (PRED element) returns non-nil in seq."
+ "Return the number of elements for which (PRED element) is non-nil in SEQ."
(let ((count 0))
(seq-doseq (elt seq)
(when (funcall pred elt)
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)
+ (let (len (errtext (format "Bad bounding indices: %s, %s" start end)))
(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)))
+ (when (> start 0)
+ (setq seq (nthcdr (1- start) seq))
+ (or seq (error "%s" errtext))
+ (setq seq (cdr seq)))
(if end
(let ((res nil))
- (while (>= (setq end (1- end)) start)
+ (while (and (>= (setq end (1- end)) start) seq)
(push (pop seq) res))
+ (or (= (1+ end) start) (error "%s" errtext))
(nreverse res))
(seq-copy seq))))
(t (error "Unsupported sequence: %s" seq))))
(`list (apply #'append (append seqs '(nil))))
(t (error "Not a sequence type name: %s" type))))
+(defun seq-mapcat (function seq &optional type)
+ "Concatenate the result of applying FUNCTION to each element of SEQ.
+The result is a sequence of type TYPE, or a list if TYPE is nil."
+ (apply #'seq-concatenate (or type 'list)
+ (seq-map function seq)))
+
+(defun seq-partition (seq n)
+ "Return a list of the elements of SEQ grouped into sub-sequences of length N.
+The last sequence may contain less than N elements. If N is a
+negative integer or 0, nil is returned."
+ (unless (< n 1)
+ (let ((result '()))
+ (while (not (seq-empty-p seq))
+ (push (seq-take seq n) result)
+ (setq seq (seq-drop seq n)))
+ (nreverse result))))
+
+(defun seq-group-by (function seq)
+ "Apply FUNCTION to each element of SEQ.
+Separate the elements of SEQ into an alist using the results as
+keys. Keys are compared using `equal'."
+ (nreverse
+ (seq-reduce
+ (lambda (acc elt)
+ (let* ((key (funcall function elt))
+ (cell (assoc key acc)))
+ (if cell
+ (setcdr cell (push elt (cdr cell)))
+ (push (list key elt) acc))
+ acc))
+ seq
+ nil)))
+
(defun seq--drop-list (list n)
- "Optimized version of `seq-drop' for lists."
+ "Return a list from LIST without its first N elements.
+This is an optimization for lists in `seq-drop'."
(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."
+ "Return a list from LIST made of its first N elements.
+This is an optimization for lists in `seq-take'."
(let ((result '()))
(while (and list (> n 0))
(setq n (1- n))
(nreverse result)))
(defun seq--drop-while-list (pred list)
- "Optimized version of `seq-drop-while' for lists."
+ "Return a list from the first element for which (PRED element) is nil in LIST.
+This is an optimization for lists in `seq-drop-while'."
(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."
+ "Return the successive elements for which (PRED element) is non-nil in LIST.
+This is an optimization for lists in `seq-take-while'."
(let ((result '()))
(while (and list (funcall pred (car list)))
(push (pop list) result))