The Kitchin Research Group

One really great feature in org-mode is you have many options to pass data between code-blocks. In this post we look at some of these options using emacs-lisp as the language. This runs in a session where you can keep variables in memory between blocks, and use them in subsequent blocks.

Here we set a variable to a value.

(setq some-variable 42)

42

Then later in another block we can use that variable:

(+ some-variable 1)

43

While you are in the session, some-variable can be used. If you want some mind-bending trouble, the emacs-lisp session is global, and you can access some-variable even in another buffer! Don't do that. When you close emacs this variable will disappear, and all that is left are the results from above.

There is another way to pass information from one block to another using named src blocks and variables in the block header. This allows you to pass data between blocks by name, and you will see later you can even access the results by name from other files.

#+name: block-1
#+BEGIN_SRC emacs-lisp
(current-time-string)
#+END_SRC

(current-time-string)

Tue Feb 12 08:19:23 2019

#+BEGIN_SRC emacs-lisp :var input=block-1
(format "We got %S in block-1" input)
#+END_SRC

(format "We got %S in block-1" input)

We got "Tue Feb 12 08:20:44 2019" in block-1

#+name: block-2
#+BEGIN_SRC emacs-lisp :cache yes
(current-time-string)
#+END_SRC

(current-time-string)

Tue Feb 12 08:06:22 2019

(format "We got %S in block-2" input)

We got "Tue Feb 12 08:06:22 2019" in block-2

(require 'json)
(json-encode `(("date" . ,(current-time-string))))

(format "We got %S in json" input)

We got "{\"date\":\"Tue Feb 12 08:30:20 2019\"}
" in json

#+BEGIN_SRC emacs-lisp :var input=./2019-02-12.org:json
input
#+END_SRC

#+RESULTS:
: {"date":"Tue Feb 12 08:30:20 2019"}

#+name: block-3
#+BEGIN_SRC emacs-lisp :cache yes :file block-3
(require 'json)
(json-encode `(("date" . ,(current-time-string))))
#+END_SRC

#+RESULTS[a14d376653bd8c40a0961ca95f21d8837dddec66]: block-3
[[file:block-3]]

(require 'json)
(json-encode `(("date" . ,(current-time-string))))

cat block-3

input

/Users/jkitchin/Box Sync/kitchingroup/jkitchin/journal/2019/02/12/block-3

(with-temp-buffer
  (insert-file-contents input)
  (format "We got %S in block-3" (json-read-from-string (buffer-string))))

We got ((date . "Tue Feb 12 08:46:55 2019")) in block-3

(with-temp-buffer
  (insert-file-contents input)
  (format "We got %S in the appendix data" (json-read-from-string (buffer-string))))

We got "{\"date\":\"Tue Feb 12 09:11:12 2019\"}" in the appendix data

(require 'json)
(let ((f "block-4.json"))
  (with-temp-file f
    (prin1
     (json-encode `(("date" . ,(current-time-string))))
     (current-buffer)))
  f)

block-4.json

cat block-4.json

(with-temp-buffer
  (insert-file-contents input)
  (format "We got %S in block-4" (json-read-from-string (buffer-string))))

We got "{\"date\":\"Tue Feb 12 08:51:25 2019\"}" in block-4

(require 'json)
(let ((f "appendix.json"))
  (with-temp-file f
    (prin1
     (json-encode `(("date" . ,(current-time-string))))
     (current-buffer)))
  f)

appendix.json

Copyright (C) 2019 by John Kitchin. See the License for information about copying.

org-mode source

Org-mode version = 9.2.1

I am a big fan of f-strings in Python 3. They let you put variable names and expressions in a string template that get expanded to create new strings. Here is a simple example of using those:

username = 'John Kitchin'
somevar = 5**0.5
print(f'{username:30s}{somevar:1.2f}')

John Kitchin                  2.24

String formatting in emacs-lisp is by comparison not as fun and easy. Out of the box we have:

(let ((username "John Kitchin")
      (somevar (sqrt 5)))
  (format "%-30s%1.2f" username somevar))

John Kitchin                  2.24

That is still three lines of code, but it is ugly and hard to read like the old python code:

print('%-30s%1.2f' % (username, somevar))

John Kitchin                  2.24

My experience has shown that this gets harder to figure out as the strings get larger, and f-strings are easier to read.

The wonderful 's library provides some salvation for emacs-lisp, if you don't want the format fields. You can refer to variables in a lexical environment like this.

(let ((username "John Kitchin")
      (somevar (sqrt 5)))
  (s-lex-format "${username}${somevar}"))

John Kitchin2.23606797749979

Today, I decided to do something about this, and wrote this little macro. It is a variation on s-lex-format that introduces a slightly new syntax. You can now add an optional format field separated from the variable name by a space.

(defmacro f-string (fmt)
  "Like `s-format' but with format fields in it.
FMT is a string to be expanded against the current lexical
environment. It is like what is used in `s-lex-format', but has
an expanded syntax to allow format-strings. For example:
${user-full-name 20s} will be expanded to the current value of
the variable `user-full-name' in a field 20 characters wide.
  (let ((f (sqrt 5)))  (f-string \"${f 1.2f}\"))
  will render as: 2.24
This function is inspired by the f-strings in Python 3.6, which I
enjoy using a lot.
"
  (let* ((matches (s-match-strings-all"${\\(?3:\\(?1:[^} ]+\\) *\\(?2:[^}]*\\)\\)}" fmt))
         (agetter (cl-loop for (m0 m1 m2 m3) in matches
                        collect `(cons ,m3  (format (format "%%%s" (if (string= ,m2 "")
                                                                      (if s-lex-value-as-lisp "S" "s")
                                                                   ,m2))
                                                  (symbol-value (intern ,m1)))))))

    `(s-format ,fmt 'aget (list ,@agetter))))

f-string

Here it is in action.

(let ((username "John Kitchin")
      (somevar (sqrt 5)))
  (f-string "${username -30s}${somevar 1.2f}"))

John Kitchin                  2.24

It still lacks some of the capability of f-strings in python, e.g. in Python, arguments inside the template to be expanded get evaluated. The solution used above is too simple for that, since it just used a regexp and is limited to the value of variables in the lexical environment.

print(f'{5**0.5:1.3f}')

2.236

Nevertheless, this simple solution matches what I do most of the time anyway, so I still consider it an improvement!

Copyright (C) 2018 by John Kitchin. See the License for information about copying.

org-mode source

Org-mode version = 9.1.13

In this issue in scimax, Robert asked if it was possible to save searches, and then to repeat them every so often and only see the new results. This needs some persistent caching of the records, and a comparison of the current search results with the previous search results.

biblio provides a nice interface to searching a range of resources for bibliographic references. In this post, I will focus on arxiv. Out of the box, biblio does not seem to support this use case, but as you will see, it has many of the pieces required to achieve it. Let's start picking those pieces apart.

(require 'biblio)

biblio

Here is the first piece we need: a way to run a query, and get results back as a data structure. Here we just look at the first result.

(let* ((query "alloy segregration")
       (backend 'biblio-arxiv-backend)
       (cb (url-retrieve-synchronously (funcall backend 'url query)))
       (results (with-current-buffer cb
                  (funcall backend 'parse-buffer))))
  (car results))

((doi . "10.1103/PhysRevB.76.014112")
 (identifier . "0704.2752v2")
 (year . "2007")
 (title . "Modelling Thickness-Dependence of Ferroelectric Thin Film Properties")
 (authors nil nil nil nil nil nil nil nil nil nil nil nil nil "L. Palova" nil "P. Chandra" nil "K. M. Rabe" nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil)
 (container . "PRB 76, 014112 (2007)")
 (category . "cond-mat.mtrl-sci")
 (references "10.1103/PhysRevB.76.014112" "0704.2752v2")
 (type . "eprint")
 (url . "https://doi.org/10.1103/PhysRevB.76.014112")
 (direct-url . "http://arxiv.org/pdf/0704.2752v2"))

Next, we need a database to store the results in. I will just use a flat file database with a file for each record. The filename will be the md5 hash of the doi or the record itself. Why is that a good idea? Well, the doi is a constant, so if it exists the md5 will also be a constant. The doi itself is not a good filename in general, but the md5 is. The md5 of the record itself will be fragile to any changes, so if it has a doi, we should use it. If it doesn't and later gets one, we should see it again since that could mean it has been published. Also, if it changes because of some new version we might want to see it again. In any case, the existence of that file will be evidence we have seen that record before, and will indicate we need to remove it from the current view.

The flat file database is not super inspired. It is modeled a little after elfeed, but other solutions might work better for large sets of records, but this approach will work fine for this post.

Here is a function that returns nil if the record has been seen, and if not, saves the record and returns it.

(defvar db-dir "~/.arxiv-db/")

(unless (f-dir? db-dir) (make-directory db-dir t))

(defun unseen-record-p (record)
  "Given a RECORD return it if it is unseen.
Also, save the record so next time it will be marked seen. A
record is seen if we have seen the DOI or the record as a string
before."
  (let* ((doi (cdr (assoc 'doi record)))
         (contents (with-temp-buffer
                     (prin1 record (current-buffer))
                     (buffer-string)))
         (hash (md5 (or doi contents)))
         (fname (expand-file-name hash db-dir)))

    (if (f-exists? fname)
        nil
      (with-temp-file fname
        (insert contents))
      record)))

unseen-record-p

Now we can use that as a filter that saves records by side effect.

(defun scimax-arxiv (query)
  (interactive "Query: ")

  (let* ((backend 'biblio-arxiv-backend)
         (cb (url-retrieve-synchronously (funcall backend 'url query)))
         (results (-filter 'unseen-record-p (with-current-buffer cb
                                              (funcall backend 'parse-buffer))))
         (results-buffer (biblio--make-results-buffer (current-buffer) query backend)))
    (with-current-buffer results-buffer
      (biblio-insert-results results ""))
    (pop-to-buffer results-buffer)))

(scimax-arxiv "alloy segregation")

#<buffer *arXiv search*>

Now, when I run that once I see something like this:

and if I run it again:

(scimax-arxiv "alloy segregation")

#<buffer *arXiv search*>

Then the buffer is empty, since we have seen all the entries before.

Here are the files in our database:

ls ~/.arxiv-db/

Here are the contents of one of those files:

(with-temp-buffer
 (insert-file-contents "~/.arxiv-db/18085fe2512e15d66addc7dfb71f7cd2")
 (read (buffer-string)))

((doi) (identifier . 1101.3464v3) (year . 2011) (title . Characterizing Solute Segregation and Grain Boundary Energy in a Binary
  Alloy Phase Field Crystal Model) (authors nil nil nil nil nil nil nil nil nil nil nil nil nil Jonathan Stolle nil Nikolas Provatas nil nil nil nil nil nil nil nil nil nil nil) (container) (category . cond-mat.mtrl-sci) (references nil 1101.3464v3) (type . eprint) (url . http://arxiv.org/abs/1101.3464v3) (direct-url . http://arxiv.org/pdf/1101.3464v3))

So, if you need to read this in again later, no problem.

Now, what could go wrong? I don't know much about how the search results from arxiv are returned. For example, this query returns 10 hits.

(let* ((query "alloy segregration")
       (backend 'biblio-arxiv-backend)
       (cb (url-retrieve-synchronously (funcall backend 'url query)))
       (results (with-current-buffer cb
                  (funcall backend 'parse-buffer))))
  (length results))

10

There is just no way there are only 10 hits for this query. So, there must be a bunch more that you get by either changing the requested number in some argument, or by using subsequent queries to get the rest of them. I don't know if there are more advanced query options with biblio, e.g. to find entries newer than the last time it was run. On the advanced search page for arxiv, it looks like there is only a by year option.

This is still a good idea, and a lot of the pieces are here,

Copyright (C) 2018 by John Kitchin. See the License for information about copying.

org-mode source

Org-mode version = 9.1.6

In Python I am used to some simple idioms like this:

print([1, 2, 3] * 2)
print("ab" * 3)

[1, 2, 3, 1, 2, 3] ababab

There is even such fanciness as defining operators for objects, as long as they have the appropriate dunder methods defined:

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __str__(self):
        return "Point ({}, {})".format(self.x, self.y)

    def __mul__(self, a):
        return Point(self.x * a, self.y * a)

    def __rmul__(self, a):
        return Point(self.x * a, self.y * a)
    
p = Point(1, 1)
print(p * 2)
print(3 * p)

Point (2, 2) Point (3, 3)

Out of the box, these things are not possible in elisp. Operators like * in elisp only take numbers or markers. We have a few options to change this. The worst option is to simply redefine these functions. That is bad because it is not reversible. We could define new functions that have the behavior we want, but then we lose the semantic meaning of "*" that we were aiming for. A better option is to advise these functions. This is reversible, because you can later unadvise them. Today we look at some strategies to do this.

We will use "around" advise because it will let us bypass the original intent of the function when we want to, or use it when we do. First, we create a function that will be the advice and add it to the * function. This first draft won't actually change the behavior of *; if all the args are numbers or markers it will simply use the original function as before.

(require 'dash)

(defun *--*-around (orig-fun &rest args)
  "if every arg is a number do *, else do something else."
  (cond
   ((-every? (lambda (x) (or (numberp x) (markerp x))) args)
    (apply orig-fun args))))

(advice-add '* :around #'*--*-around)

Let's just confirm

(* 1 2 3)

6

Now, we can start modifying our function to handle some other cases. Let's do the list and string first. The * function is variadic, but in these cases it makes sense to limit to two arguments. We need two cases for each type since we can write (* 2 list) or (* list 2). We also should create a fall-through case that raises an error to alert us we can't multiply things.

(defun *--*-around (orig-fun &rest args)
  "if every arg is a number do *, else do something else."
  (cond
   ;; The original behavior
   ((-every? (lambda (x) (or (numberp x) (markerp x))) args)
    (apply orig-fun args))

   ;; create repeated copies of list
   ((and (listp (first args))
         (integerp (second args))
         (= 2 (length args)))
    (loop for i from 0 below (second args) append (copy-list (first args))))

   ((and (integerp (first args))
         (listp (second args))
         (= 2 (length args)))
    (loop for i from 0 below (first args) append (copy-list (second args))))

   ;; Make repeated string
   ((and (stringp (first args))
         (integerp (second args))
         (= 2 (length args)))
    (loop for i from 0 below (second args) concat (first args)))

   ((and (integerp (first args))
         (stringp (second args))
         (= 2 (length args)))
    (loop for i from 0 below (first args) concat (second args)))

   (t
    (error "You cannot * %s" args))))

*--*-around

Here is the new advice in action.

(list
 (* '(a b) 2)
 (* 2 '(c d))
 (* 2 "ab")
 (* "cd" 2))

That captures the spirit of overloading * for lists and strings. What about that object example? We have to make some assumptions here. Python looks for an uses a dunder mul method. We will assume a double dash method (–mul–) in a similar spirit. We have to modify the advice one final time. We just add a condition to check if one of the arguments is an eieio-object, and then call the –mul– function on the arguments.

(defun *--*-around (orig-fun &rest args)
  "if every arg is a number do *, else do something else."
  (cond
   ;; The original behavior
   ((-every? (lambda (x) (or (numberp x) (markerp x))) args)
    (apply orig-fun args))

   ;; create repeated copies of list
   ((and (listp (first args))
         (integerp (second args))
         (= 2 (length args)))
    (loop for i from 0 below (second args) append (copy-list (first args))))

   ((and (integerp (first args))
         (listp (second args))
         (= 2 (length args)))
    (loop for i from 0 below (first args) append (copy-list (second args))))

   ;; Make repeated string
   ((and (stringp (first args))
         (integerp (second args))
         (= 2 (length args)))
    (loop for i from 0 below (second args) concat (first args)))

   ((and (integerp (first args))
         (stringp (second args))
         (= 2 (length args)))
    (loop for i from 0 below (first args) concat (second args)))

   ;; Handle object
   ((or (and (eieio-object-p (first args))
             (numberp (second args)))
        (and (numberp (first args))
             (eieio-object-p (second args))))
    (apply '--mul-- args))

   (t
    (error "You cannot * %s" args))))

*--*-around

Now, we can define a class and the –mul– function and show that our overloaded * function works. Note we can define two signatures of –mul– so it is not necessary to define an –rmul– in this case as it was with Python (although we still create two functions in the end).

(require 'eieio)

(defclass Point ()
  ((x :initarg :x)
   (y :initarg :y)))

(cl-defmethod --mul-- ((p Point) a)
  (Point :x (* (oref p :x) a) :y (* (oref p :y) a)))

(cl-defmethod --mul-- (a (p Point))
  (Point :x (* (oref p :x) a) :y (* (oref p :y) a)))

(cl-defmethod --str-- ((p Point))
  (format "Point (%s, %s)" (oref p :x) (oref p :y)))

(let ((P (Point :x 1 :y 1)))
  (list
   (--str-- (* P 2))
   (--str-- (* 3 P))))

That is pretty awesome. Before going on, here is how you remove the advice:

(advice-remove '* '*--*-around)

This example has been pretty instructive. You have to handle overloading for all the intrinsic types. We did lists and strings here; you might also consider vectors. For objects, it looks like we can at least try using a generic method like –mul–. One detail I neglected to consider here is that * is natively variadic. For these special cases, we did not implement variadic versions. This isn't a feature of Python which uses infix notation, so every call is with two arguments. In some cases it might make sense to support variadic args, but that seems like a generally challenging thing to do. While (* "a" 2 3) might be expected to create a string of "aaaaaa", (* "a" 2 '(3)) doesn't make sense at all.

It would be straightforward to extend this to other operators like '+ to concatenate strings, lists and vectors, or '- to remove chars or elements, including extensions to objects using double-dash functions like –add–, –subtract–, etc. Another nice idea might be to advise print to use –str– on objects.

On the surface this looks useful so far. Python defines a lot of dunder methods that cover all kinds of scenarios including logical comparisons, bit shifting, mod, incrementing operators, casting, comparisons, right/left operations, indexing and assignment, length and others. That would be a lot of advices. This approach is moderately tedious to expand though; you have to keep adding conditional cases.

An alternative to the big conditional statement used in the advice might be the use of a generic function. With this approach we define a generic function that just does multiplication by default. Then we define specific cases with specific signatures that are used for lists, strings, objects, etc. That is basically all our conditional above was doing, matching signatures and executing a chunk of code accordingly.

Here is our default case that does the original behavior. We still use advice to apply the function.

(cl-defgeneric generic-multiply (orig-fun &rest args)
  "Generic multiply for when no specific case exists."
  (apply orig-fun args))

(defun *--*-around-generic (orig-fun &rest args)
  (apply 'generic-multiply orig-fun args))

(advice-add '* :around #'*--*-around-generic)

That should just work as usual for regular multiplication.

(* 1 2 3 4)

24

Sure enough it does. Now, we can define a specific method for a string. We need a specialized method for each signature, e.g. pre and post multiplication.

(cl-defmethod generic-multiply ((orig-fun subr) (s string) (n integer))
  (loop for i from 0 below n concat s))

(cl-defmethod generic-multiply ((orig-fun subr) (n integer) (s string))
  (loop for i from 0 below n concat s))

(list
 (* "Ac" 2)
 (* 2 "Ad"))

That works fine, and we did not have to modify our original advice function at all! Next the list:

(cl-defmethod generic-multiply ((orig-fun subr) (L list) (n integer))
  (loop for i from 0 below n append (copy-list L)))

(cl-defmethod generic-multiply ((orig-fun subr) (n integer) (L list))
  (loop for i from 0 below n append (copy-list L)))

(list (* '(1 2) 2)
      (* 2 '(3 4)))

That also works fine. Last, our class example. This should work on all objects I think (unless there is some way to make classes that do not inherit the default superclass).

(cl-defmethod generic-multiply ((orig-fun subr) (n integer) (obj eieio-default-superclass))
  (--mul-- n obj))

(cl-defmethod generic-multiply ((orig-fun subr) (obj eieio-default-superclass) (n integer))
  (--mul-- n obj))

(let ((P (Point :x 1 :y 1)))
  (list
   (--str-- (* P 2))
   (--str-- (* 3 P))))

This is a much better approach to extending the multiplication operator! If I continue this path in the future I would probably take this one. This could be useful to make elisp more like some more popular contemporary languages like Python, as well as to add linear algebra like notation or mathematical operations on objects in elisp. It kind of feels like these operations ought to be generic functions to start with to make this kind of overloading easier from the beginning. Functions like "*" are currently defined in the C source code though, maybe for performance reasons. It is not obvious what the consequences of making them generic might be.

(defun to-be-bytten (p1 n)
  (* p1 n))

to-be-bytten

(to-be-bytten (Point :x 1 :y 1) 2)

[eieio-class-tag--Point 2 2]

(byte-compile 'to-be-bytten)

(condition-case err
    (to-be-bytten (Point :x 1 :y 1) 2)
  ((error r)
   (message "Doh! Christopher was right. It did not work...\n%s" err)))

Doh! Christopher was right. It did not work...
(wrong-type-argument number-or-marker-p [eieio-class-tag--Point 1 1])

Copyright (C) 2017 by John Kitchin. See the License for information about copying.

org-mode source

Org-mode version = 9.0.7

Emacs lisp has a few data structures that store key-value pairs. Here are some canonical examples of these data structures and the way to get data out of them.

• a-lists

(let ((data '((key1 . 4)
              (key2 . "tree"))))
  (cdr (assoc 'key2 data)))

tree

• p-lists

(let ((data '(:key1 4 :key2 "tree")))
  (plist-get data :key2))

tree

• A hash table

(let ((data #s(hash-table data (key1 4 key2 "tree"))))
  (gethash 'key2 data))

tree

Each of these uses some function to get data out of them. I have been learning about closures today, and realized a way you can make a "callable" data structure using them. In a closure, the data is stored as part of a function. We will use a "let over lambda" with a defalias in a lexical environment to achieve this. I will wrap a p-list with this approach, but it could work with any of the examples above. We will make the function have a few behaviors that allow us to see the whole data structure with no args, to get a value with one arg that is a key, and to set a value if there are more than two args add them as key-val pairs to the data structure. This block binds the function to the symbol "d" which is then a callable function.

(let ((data '(:key1 4 :key2 "tree")))
  (defalias 'd
    (lambda (&rest key-vals)
      (cond
       ;; no args, return data
       ((= 0 (length key-vals))
        data)
       ;; just a key, get val
       ((= 1 (length key-vals))
        (plist-get data (car key-vals)))
       (t
        (loop for key in (-slice key-vals 0 nil 2)
              for val in (-slice key-vals 1 nil 2)
              do
              (plist-put data key val))
        data)))))

d

Now we can use it like to get some data out:

(d :key2)

tree

And add new values like:

(d :key3 "oak")

You can update a value with this too:

(d :key3 "pine")

or add multiple values like this:

(d :key4 0 :key5 9)

And see the whole plist with no args:

(d)

Pretty nice! It seems like there ought to be a macro to facilitate creating those. Here is one. This macro basically expands to the same code as above, but for fun I add a default value option.

(defmacro default-dict (var &optional default &rest key-vals)
  "Bind a callable plist to VAR that contains KEY-VALS."
  (let ()
    `(let ((data ',key-vals))
       (defalias ',var
         (lambda (&rest key-vals)
           (message "%s" key-vals)
           (cond
            ;; no args, return data
            ((= 0 (length key-vals))
             data)
            ;; just a key, get val
            ((= 1 (length key-vals))
             (or  (plist-get data (car key-vals)) ,default))
            (t
             (loop for key in (-slice key-vals 0 nil 2)
                   for val in (-slice key-vals 1 nil 2)
                   do
                   (plist-put data key val))
             data)))))))

Here is an instance of it.

(default-dict d2 "None" :key1 4 :key2 "tree")

d2

And here it is in use.

(d2 :key1)

4

(d2 :new-key)

None

Not bad. If you come from Python, you might find this style of data structure to be more similar to what you are used to seeing. It sure seems less verbose than the usual plist boilerplate I have used before.

(defmacro with-dict (key-vals &rest body)
  "A context-manager for a plist where each key is a callable
function that returns the value."
  (declare (indent 1))
  (let* ((g (if (symbolp key-vals)
                (symbol-value key-vals)
              key-vals))
         (keys (-slice g 0 nil 2)))
    `(labels ,(loop for key in keys
                    collect
                    (list key '() `(plist-get ',g  ,key)))
       ,@body)))

with-dict

(with-dict (:a 1 :b 'some-symbol :c 3)
  (:b))

(let ((d '(:key1 1 :key2 some-other-symbol :key3 3)))
  (with-dict d
    (format "We got %s" (:key2))))

We got some-other-symbol

(defmacro with-plist-vals (plist &rest body)
  "Bind the values of a plist to variables with the name of the keys."
  (declare (indent 1))
  `(let ,(loop for key in (-slice plist 0 nil 2)
               for val in (-slice plist 1 nil 2)
               collect (list (intern
                              (substring (symbol-name key) 1))
                             val))
     ,@body))

with-plist-vals

(with-plist-vals (:a 4 :b 6)
 (* 2 a))

8

Copyright (C) 2018 by John Kitchin. See the License for information about copying.

org-mode source

Org-mode version = 9.1.6