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[elpa] master 77b60ce 1/2: packages/let-alist: Enable access to deeper a
From: |
Artur Malabarba |
Subject: |
[elpa] master 77b60ce 1/2: packages/let-alist: Enable access to deeper alists |
Date: |
Sat, 20 Dec 2014 16:54:01 +0000 |
branch: master
commit 77b60ce4aa135d3a08af0bbdce695b5aff112d8d
Author: Artur Malabarba <address@hidden>
Commit: Artur Malabarba <address@hidden>
packages/let-alist: Enable access to deeper alists
---
packages/let-alist/let-alist.el | 77 +++++++++++++++++++++++++++++----------
1 files changed, 58 insertions(+), 19 deletions(-)
diff --git a/packages/let-alist/let-alist.el b/packages/let-alist/let-alist.el
index 2efa027..692beba 100644
--- a/packages/let-alist/let-alist.el
+++ b/packages/let-alist/let-alist.el
@@ -4,7 +4,7 @@
;; Author: Artur Malabarba <address@hidden>
;; Maintainer: Artur Malabarba <address@hidden>
-;; Version: 1.0.1
+;; Version: 1.0.2
;; Keywords: extensions lisp
;; Prefix: let-alist
;; Separator: -
@@ -39,21 +39,25 @@
;; (let-alist alist
;; (if (and .title .body)
;; .body
-;; .site))
+;; .site
+;; .site.contents))
;;
-;; expands to
+;; essentially expands to
;;
;; (let ((.title (cdr (assq 'title alist)))
-;; (.body (cdr (assq 'body alist)))
-;; (.site (cdr (assq 'site alist))))
+;; (.body (cdr (assq 'body alist)))
+;; (.site (cdr (assq 'site alist)))
+;; (.site.contents (cdr (assq 'contents (cdr (assq 'site alist))))))
;; (if (and .title .body)
;; .body
-;; .site))
+;; .site
+;; .site.contents))
+;;
+;; If you nest `let-alist' invocations, the inner one can't access
+;; the variables of the outer one. You can, however, access alists
+;; inside the original alist by using dots inside the symbol, as
+;; displayed in the example above by the `.site.contents'.
;;
-;; Note that only one level is supported. If you nest `let-alist'
-;; invocations, the inner one can't access the variables of the outer
-;; one.
-
;;; Code:
@@ -70,8 +74,33 @@ symbol, and each cdr is the same symbol without the `.'."
(list (cons data (intern (replace-match "" nil nil name)))))))
((not (listp data)) nil)
(t (apply #'append
- (remove nil (mapcar #'let-alist--deep-dot-search data))))))
+ (mapcar #'let-alist--deep-dot-search data)))))
+
+(defun let-alist--access-sexp (symbol variable)
+ "Return a sexp used to acess SYMBOL inside VARIABLE."
+ (let* ((clean (let-alist--remove-dot symbol))
+ (name (symbol-name clean)))
+ (if (string-match "\\`\\." name)
+ clean
+ (let-alist--list-to-sexp
+ (mapcar #'intern (nreverse (split-string name "\\.")))
+ variable))))
+
+(defun let-alist--list-to-sexp (list var)
+ "Turn symbols LIST into recursive calls to `cdr' `assq' on VAR."
+ `(cdr (assq ',(car list)
+ ,(if (cdr list) (let-alist--list-to-sexp (cdr list) var)
+ var))))
+
+(defun let-alist--remove-dot (symbol)
+ "Return SYMBOL, sans an initial dot."
+ (let ((name (symbol-name symbol)))
+ (if (string-match "\\`\\." name)
+ (intern (replace-match "" nil nil name))
+ symbol)))
+
+;;; The actual macro.
;;;###autoload
(defmacro let-alist (alist &rest body)
"Let-bind dotted symbols to their cdrs in ALIST and execute BODY.
@@ -83,20 +112,30 @@ For instance, the following code
(let-alist alist
(if (and .title .body)
.body
- .site))
+ .site
+ .site.contents))
-expands to
+essentially expands to
(let ((.title (cdr (assq 'title alist)))
- (.body (cdr (assq 'body alist)))
- (.site (cdr (assq 'site alist))))
+ (.body (cdr (assq 'body alist)))
+ (.site (cdr (assq 'site alist)))
+ (.site.contents (cdr (assq 'contents (cdr (assq 'site alist))))))
(if (and .title .body)
.body
- .site))"
+ .site
+ .site.contents))
+
+If you nest `let-alist' invocations, the inner one can't access
+the variables of the outer one. You can, however, access alists
+inside the original alist by using dots inside the symbol, as
+displayed in the example above."
(declare (indent 1) (debug t))
- `(let ,(mapcar (lambda (x) `(,(car x) (cdr (assq ',(cdr x) ,alist))))
- (delete-dups (let-alist--deep-dot-search body)))
- ,@body))
+ (let ((var (gensym "alist")))
+ `(let ((,var ,alist))
+ (let ,(mapcar (lambda (x) `(,(car x) ,(let-alist--access-sexp (car x)
var)))
+ (delete-dups (let-alist--deep-dot-search body)))
+ ,@body))))
(provide 'let-alist)
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