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New macro seq-let, providing destructuring support to seq.el

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* lisp/emacs-lisp/seq.el (seq-let): New macro.  `seq-let' is similar
to `cl-destructuring-bind' but works on all sequence types supported
by `seq.el'.  Bump version number to 1.6.
* test/automated/seq-tests.el: Add tests for seq-let.
* doc/lispref/sequences.texi: Add documentation for seq-let.
This commit is contained in:
Nicolas Petton 2015-05-01 19:30:56 +02:00
parent b0481de73b
commit c856843f6b
3 changed files with 81 additions and 2 deletions
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39
lisp/emacs-lisp/seq.el
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@ -4,7 +4,7 @@
;; Author: Nicolas Petton <nicolas@petton.fr>
;; Keywords: sequences
;; Version: 1.5
;; Version: 1.6
;; Package: seq
;; Maintainer: emacs-devel@gnu.org
@ -40,6 +40,10 @@
;;
;; All functions are tested in test/automated/seq-tests.el
;;; TODO:
;; - Add support for &rest in the argument list of seq-let
;;; Code:
(defmacro seq-doseq (spec &rest body)
@ -65,6 +69,14 @@ Evaluate BODY with VAR bound to each element of SEQ, in turn.
(pop ,index))))
,@body)))))
(defmacro seq-let (args seq &rest body)
"Bind the variables in ARGS to the elements of SEQ then evaluate BODY."
(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.
@ -336,7 +348,30 @@ This is an optimization for lists in `seq-take-while'."
(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\\>")))
(defun seq--make-bindings (args seq &optional initial-bindings)
"Return an alist of the bindings the variables in ARGS to the elements of SEQ.
if INITIAL-BINDINGS is non-nil, append new bindings to it, and
return INITIAL-BINDINGS."
(let ((index 0))
(seq-doseq (name args)
(if (sequencep name)
(setq initial-bindings (seq--make-bindings
(seq--elt-safe args index)
`(seq--elt-safe ,seq ,index)
initial-bindings))
(push `(,name (seq--elt-safe ,seq ,index)) initial-bindings))
(setq index (1+ index)))
initial-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)))
(defalias 'seq-copy #'copy-sequence)
(defalias 'seq-elt #'elt)