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[Emacs-diffs] map 988d721: Add a pcase pattern for maps and `map-let' ba
From: |
Nicolas Petton |
Subject: |
[Emacs-diffs] map 988d721: Add a pcase pattern for maps and `map-let' based on it |
Date: |
Tue, 02 Jun 2015 20:19:56 +0000 |
branch: map
commit 988d72118687758af6c2b7c56c80056630d428ca
Author: Nicolas Petton <address@hidden>
Commit: Nicolas Petton <address@hidden>
Add a pcase pattern for maps and `map-let' based on it
* lisp/emacs-lisp/map.el (map-let): New macro.
(map--make-pcase-bindings, map--make-pcase-patterns): New functions.
* test/automated/map-tests.el: New test for `map-let'.
---
lisp/emacs-lisp/map.el | 35 +++++++++++++++++++++++++++++++++++
test/automated/map-tests.el | 12 ++++++++++++
2 files changed, 47 insertions(+), 0 deletions(-)
diff --git a/lisp/emacs-lisp/map.el b/lisp/emacs-lisp/map.el
index 8801b2a..dea2abc 100644
--- a/lisp/emacs-lisp/map.el
+++ b/lisp/emacs-lisp/map.el
@@ -44,6 +44,24 @@
(require 'seq)
+(pcase-defmacro map (&rest args)
+ "pcase pattern matching map elements.
+Matches if the object is a map (list, hash-table or array), and
+binds values from ARGS to the corresponding element of the map.
+
+ARGS can be an alist of key/binding pairs of a list of keys."
+ `(and (pred map-p)
+ ,@(map--make-pcase-bindings args)))
+
+(defmacro map-let (args map &rest body)
+ "Bind the variables in ARGS to the elements of MAP then evaluate BODY.
+
+ARGS can be an alist of key/binding pairs or a list of keys. MAP
+can be a list, hash-table or array."
+ (declare (indent 2) (debug t))
+ `(pcase-let ((,(map--make-pcase-patterns args) ,map))
+ ,@body))
+
(defun map-elt (map key &optional default)
"Perform a lookup in MAP of KEY and return its associated value.
If KEY is not found, return DEFAULT which defaults to nil.
@@ -331,5 +349,22 @@ If KEY is not found, return DEFAULT which defaults to nil."
map)
ht))
+(defun map--make-pcase-bindings (args)
+ "Return a list of pcase bindings from ARGS to the elements of a map."
+ (seq-map (lambda (elt)
+ (if (consp elt)
+ `(app (pcase--flip map-elt ',(car elt)) ,(cdr elt))
+ `(app (pcase--flip map-elt ',elt) ,elt)))
+ args))
+
+(defun map--make-pcase-patterns (args)
+ "Return a list of `(map ...)' pcase patterns built from ARGS."
+ (cons 'map
+ (seq-map (lambda (elt)
+ (if (and (consp elt) (eq 'map (car elt)))
+ (map--make-pcase-patterns elt)
+ elt))
+ args)))
+
(provide 'map)
;;; map.el ends here
diff --git a/test/automated/map-tests.el b/test/automated/map-tests.el
index e65af89..2f7d4eb 100644
--- a/test/automated/map-tests.el
+++ b/test/automated/map-tests.el
@@ -317,5 +317,17 @@ Evaluate BODY for each created map.
(assert (map-empty-p (map-into nil 'hash-table)))
(should-error (map-into [1 2 3] 'string))))
+(ert-deftest test-map-let ()
+ (map-let (foo bar baz) '((foo . 1) (bar . 2))
+ (assert (= foo 1))
+ (assert (= bar 2))
+ (assert (null baz)))
+ (map-let ((foo . a)
+ (bar . b)
+ (baz . c)) '((foo . 1) (bar . 2))
+ (assert (= a 1))
+ (assert (= b 2))
+ (assert (null c))))
+
(provide 'map-tests)
;;; map-tests.el ends here
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