1 files changed, 69 insertions, 12 deletions
diff --git a/lisp/emacs-lisp/seq.el b/lisp/emacs-lisp/seq.el
index 904aad0afef..74510244be7 100644
--- a/lisp/emacs-lisp/seq.el
+++ b/lisp/emacs-lisp/seq.el
@@ -4,7 +4,7 @@
 
 ;; Author: Nicolas Petton <nicolas@petton.fr>
 ;; Keywords: sequences
-;; Version: 2.3
+;; Version: 2.19
 ;; Package: seq
 
 ;; Maintainer: emacs-devel@gnu.org
@@ -87,7 +87,7 @@ given, and the match does not fail."
 
 ARGS can also include the `&rest' marker followed by a variable
 name to be bound to the rest of SEQUENCE."
-  (declare (indent 2) (debug t))
+  (declare (indent 2) (debug (sexp form body)))
   `(pcase-let ((,(seq--make-pcase-patterns args) ,sequence))
      ,@body))
 
@@ -117,6 +117,16 @@ Return SEQUENCE."
 
 (defalias 'seq-each #'seq-do)
 
+(defun seq-do-indexed (function sequence)
+  "Apply FUNCTION to each element of SEQUENCE and return nil.
+Unlike `seq-map', FUNCTION takes two arguments: the element of
+the sequence, and its index within the sequence."
+  (let ((index 0))
+    (seq-do (lambda (elt)
+               (funcall function elt index)
+               (setq index (1+ index)))
+             sequence)))
+
 (cl-defgeneric seqp (sequence)
   "Return non-nil if SEQUENCE is a sequence, nil otherwise."
   (sequencep sequence))
@@ -144,6 +154,18 @@ if positive or too small if negative)."
             sequence)
     (nreverse result)))
 
+(defun seq-map-indexed (function sequence)
+  "Return the result of applying FUNCTION to each element of SEQUENCE.
+Unlike `seq-map', FUNCTION takes two arguments: the element of
+the sequence, and its index within the sequence."
+  (let ((index 0))
+    (seq-map (lambda (elt)
+               (prog1
+                   (funcall function elt index)
+                 (setq index (1+ index))))
+             sequence)))
+
+
 ;; faster implementation for sequences (sequencep)
 (cl-defmethod seq-map (function (sequence sequence))
   (mapcar function sequence))
@@ -156,7 +178,8 @@ Return a list of the results.
 
 \(fn FUNCTION SEQUENCES...)"
   (let ((result nil)
-        (sequences (seq-map (lambda (s) (seq-into s 'list))
+        (sequences (seq-map (lambda (s)
+                              (seq-into s 'list))
                             (cons sequence sequences))))
     (while (not (memq nil sequences))
       (push (apply function (seq-map #'car sequences)) result)
@@ -206,6 +229,16 @@ The result is a sequence of the same type as SEQUENCE."
 (cl-defmethod seq-sort (pred (list list))
   (sort (seq-copy list) pred))
 
+(defun seq-sort-by (function pred sequence)
+  "Sort SEQUENCE using PRED as a comparison function.
+Elements of SEQUENCE are transformed by FUNCTION before being
+sorted.  FUNCTION must be a function of one argument."
+  (seq-sort (lambda (a b)
+              (funcall pred
+                       (funcall function a)
+                       (funcall function b)))
+            sequence))
+
 (cl-defgeneric seq-reverse (sequence)
   "Return a sequence with elements of SEQUENCE in reverse order."
   (let ((result '()))
@@ -240,9 +273,9 @@ of sequence."
 TYPE can be one of the following symbols: vector, string or
 list."
   (pcase type
-    (`vector (vconcat sequence))
-    (`string (concat sequence))
-    (`list (append sequence nil))
+    (`vector (seq--into-vector sequence))
+    (`string (seq--into-string sequence))
+    (`list (seq--into-list sequence))
     (_ (error "Not a sequence type name: %S" type))))
 
 (cl-defgeneric seq-filter (pred sequence)
@@ -284,7 +317,8 @@ If SEQUENCE is empty, return INITIAL-VALUE and FUNCTION is not called."
     t))
 
 (cl-defgeneric seq-some (pred sequence)
-  "Return the first value for which if (PRED element) is non-nil for in SEQUENCE."
+  "Return non-nil if PRED is satisfied for at least one element of SEQUENCE.
+If so, return the first non-nil value returned by PRED."
   (catch 'seq--break
     (seq-doseq (elt sequence)
       (let ((result (funcall pred elt)))
@@ -317,7 +351,8 @@ found or not."
   "Return the first element in SEQUENCE that is equal to ELT.
 Equality is defined by TESTFN if non-nil or by `equal' if nil."
   (seq-some (lambda (e)
-              (funcall (or testfn #'equal) elt e))
+              (when (funcall (or testfn #'equal) elt e)
+                e))
             sequence))
 
 (cl-defgeneric seq-position (sequence elt &optional testfn)
@@ -443,16 +478,20 @@ SEQUENCE must be a sequence of numbers or markers."
   "Return element of SEQUENCE at the index N.
 If no element is found, return nil."
   (ignore-errors (seq-elt sequence n)))
+
+(cl-defgeneric seq-random-elt (sequence)
+  "Return a random element from SEQUENCE.
+Signal an error if SEQUENCE is empty."
+  (if (seq-empty-p sequence)
+      (error "Sequence cannot be empty")
+    (seq-elt sequence (random (seq-length sequence)))))
 
 
 ;;; Optimized implementations for lists
 
 (cl-defmethod seq-drop ((list list) n)
   "Optimized implementation of `seq-drop' for lists."
-  (while (and list (> n 0))
-    (setq list (cdr list)
-          n (1- n)))
-  list)
+  (nthcdr n list))
 
 (cl-defmethod seq-take ((list list) n)
   "Optimized implementation of `seq-take' for lists."
@@ -473,6 +512,24 @@ If no element is found, return nil."
   (null list))
 
 
+(defun seq--into-list (sequence)
+  "Concatenate the elements of SEQUENCE into a list."
+  (if (listp sequence)
+      sequence
+    (append sequence nil)))
+
+(defun seq--into-vector (sequence)
+  "Concatenate the elements of SEQUENCE into a vector."
+  (if (vectorp sequence)
+      sequence
+    (vconcat sequence)))
+
+(defun seq--into-string (sequence)
+  "Concatenate the elements of SEQUENCE into a string."
+  (if (stringp sequence)
+      sequence
+    (concat sequence)))
+
 (defun seq--activate-font-lock-keywords ()
   "Activate font-lock keywords for some symbols defined in seq."
   (font-lock-add-keywords 'emacs-lisp-mode