;; Author: Nicolas Petton <nicolas@petton.fr>
;; Keywords: sequences
-;; Version: 1.5
+;; Version: 1.7
;; Package: seq
;; Maintainer: emacs-devel@gnu.org
(pop ,index))))
,@body)))))
+(if (fboundp 'pcase-defmacro)
+ ;; Implementation of `seq-let' based on a `pcase'
+ ;; pattern. Requires Emacs>=25.1.
+ (progn
+ (pcase-defmacro seq (&rest args)
+ "pcase pattern matching sequence elements.
+Matches if the object is a sequence (list, string or vector), and
+binds each element of ARGS to the corresponding element of the
+sequence."
+ `(and (pred seq-p)
+ ,@(seq--make-pcase-bindings args)))
+
+ (defmacro seq-let (args seq &rest body)
+ "Bind the variables in ARGS to the elements of SEQ then evaluate BODY.
+
+ARGS can also include the `&rest' marker followed by a variable
+name to be bound to the rest of SEQ."
+ (declare (indent 2) (debug t))
+ `(pcase-let ((,(seq--make-pcase-patterns args) ,seq))
+ ,@body)))
+
+ ;; Implementation of `seq-let' compatible with Emacs<25.1.
+ (defmacro seq-let (args seq &rest body)
+ "Bind the variables in ARGS to the elements of SEQ then evaluate BODY.
+
+ARGS can also include the `&rest' marker followed by a variable
+name to be bound to the rest of SEQ."
+ (declare (indent 2) (debug t))
+ (let ((seq-var (make-symbol "seq")))
+ `(let* ((,seq-var ,seq)
+ ,@(seq--make-bindings args seq-var))
+ ,@body))))
+
(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.
(setq n (+ 1 n)))
n))
+(defun seq--make-pcase-bindings (args)
+ "Return a list of bindings of the variables in ARGS to the elements of a sequence."
+ (let ((bindings '())
+ (index 0)
+ (rest-marker nil))
+ (seq-doseq (name args)
+ (unless rest-marker
+ (pcase name
+ (`&rest
+ (progn (push `(app (pcase--flip seq-drop ,index)
+ ,(seq--elt-safe args (1+ index)))
+ bindings)
+ (setq rest-marker t)))
+ (t
+ (push `(app (pcase--flip seq--elt-safe ,index) ,name) bindings))))
+ (setq index (1+ index)))
+ bindings))
+
+(defun seq--make-pcase-patterns (args)
+ "Return a list of `(seq ...)' pcase patterns from the argument list ARGS."
+ (cons 'seq
+ (seq-map (lambda (elt)
+ (if (seq-p elt)
+ (seq--make-pcase-patterns elt)
+ elt))
+ args)))
+
+;; Helper function for the Backward-compatible version of `seq-let'
+;; for Emacs<25.1.
+(defun seq--make-bindings (args seq &optional bindings)
+ "Return a list of bindings of the variables in ARGS to the elements of a sequence.
+if BINDINGS is non-nil, append new bindings to it, and return
+BINDINGS."
+ (let ((index 0)
+ (rest-marker nil))
+ (seq-doseq (name args)
+ (unless rest-marker
+ (pcase name
+ ((pred seq-p)
+ (setq bindings (seq--make-bindings (seq--elt-safe args index)
+ `(seq--elt-safe ,seq ,index)
+ bindings)))
+ (`&rest
+ (progn (push `(,(seq--elt-safe args (1+ index))
+ (seq-drop ,seq ,index))
+ bindings)
+ (setq rest-marker t)))
+ (t
+ (push `(,name (seq--elt-safe ,seq ,index)) bindings))))
+ (setq index (1+ index)))
+ bindings))
+
+(defun seq--elt-safe (seq n)
+ "Return element of SEQ at the index N.
+If no element is found, return nil."
+ (when (or (listp seq)
+ (and (sequencep seq)
+ (> (seq-length seq) n)))
+ (seq-elt seq n)))
+
(defun seq--activate-font-lock-keywords ()
"Activate font-lock keywords for some symbols defined in seq."
(font-lock-add-keywords 'emacs-lisp-mode
- '("\\<seq-doseq\\>")))
+ '("\\<seq-doseq\\>" "\\<seq-let\\>")))
(defalias 'seq-copy #'copy-sequence)
(defalias 'seq-elt #'elt)
(defalias 'seq-do #'mapc)
(defalias 'seq-each #'seq-do)
(defalias 'seq-map #'mapcar)
+(defalias 'seq-p #'sequencep)
(unless (fboundp 'elisp--font-lock-flush-elisp-buffers)
;; In Emacsā„25, (via elisp--font-lock-flush-elisp-buffers and a few others)