funny emacs-lisp macro behavior in org-babel related to lexical-binding

funny emacs-lisp macro behavior in org-babel related to lexical-binding

[John Kitchin]

Hi all,

I was playing around with elisp macros in an org-file and came across a
behavior I didn't expect that is due to lexical binding.

Here is the code:

#+BEGIN_SRC emacs-lisp :results output :prologue
;; -*- lexical-binding: t -*-

;; you need this to make the binding.
(setq lexical-binding t)

;; Graham's alambda
(defmacro alambda (parms &rest body)
  `(cl-labels ((self ,parms ,@body))
     #'self))

(setq
 N
 (alambda (n)
          (if (> n 0)
              (cons
               n
               (self (- n 1))))))


(funcall N 3)
#+END_SRC

The last line should return (3 2 1), and it does if I use C-x C-e on
each form. If I try to run the block though, I get an error:

cons: Symbol’s value as variable is void: --cl-self--

I can see where that comes from. The macro expands to:
(lambda (n) (if (> n 0) (cons n (funcall --cl-self-- (- n 1)))))

This doesn't work because babel simply evals the body of the code. It
turns out you can use eval with lexical scoping:

(eval FORM &optional LEXICAL)

Evaluate FORM and return its value.
If LEXICAL is t, evaluate using lexical scoping.

So, I would like to propose adding the third argument to the eval
statement that reads 

(assoc :lexical params)

to turn on lexical eval if you want it.

What do you think?

--
Professor John Kitchin
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu

Re: funny emacs-lisp macro behavior in org-babel related to lexical-binding

[Nicolas Goaziou]

Hello,

John Kitchin <jkitchin@andrew.cmu.edu> writes:

> So, I would like to propose adding the third argument to the eval
> statement that reads 
>
> (assoc :lexical params)
>
> to turn on lexical eval if you want it.
>
> What do you think?

I assume you're talking about ob-emacs-lisp.el. This sounds like a good
idea. However, I suggest to make lexical binding the default value, to
be on par with the rest of Emacs.


Regards,

-- 
Nicolas Goaziou

Re: funny emacs-lisp macro behavior in org-babel related to lexical-binding

[John Kitchin]

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That sounds fine to me. Would you then use

:lexical nil

in a header to turn it off? or a new custom variable?

John

-----------------------------------
Professor John Kitchin
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu


On Fri, Apr 15, 2016 at 4:49 PM, Nicolas Goaziou <mail@nicolasgoaziou.fr>
wrote:

> Hello,
>
> John Kitchin <jkitchin@andrew.cmu.edu> writes:
>
> > So, I would like to propose adding the third argument to the eval
> > statement that reads
> >
> > (assoc :lexical params)
> >
> > to turn on lexical eval if you want it.
> >
> > What do you think?
>
> I assume you're talking about ob-emacs-lisp.el. This sounds like a good
> idea. However, I suggest to make lexical binding the default value, to
> be on par with the rest of Emacs.
>
>
> Regards,
>
> --
> Nicolas Goaziou
>

[-- Attachment #2: Type: text/html, Size: 1727 bytes --]

Re: funny emacs-lisp macro behavior in org-babel related to lexical-binding

[Nicolas Goaziou]

John Kitchin <jkitchin@andrew.cmu.edu> writes:

> That sounds fine to me. Would you then use
>
> :lexical nil

Sure. However, Babel uses "yes" and "no" as booleans so we also need to
support these. nil and t are fine too, obviously.

You would need to define a new defconst
`org-babel-header-args:emacs-lisp' to specify allowed values
for :lexical.

Also, this should probably be documented somewehere.


Regards,

Re: funny emacs-lisp macro behavior in org-babel related to lexical-binding

[John Kitchin]

I submitted a patch for this. I still am not sure I did it quite right.
Is there a page anywhere that outlines what to do?

e.g.

create a branch, make changes, how to make patches, and mail them etc...
or some other preferred method?

thanks,

Nicolas Goaziou writes:

> John Kitchin <jkitchin@andrew.cmu.edu> writes:
>
>> That sounds fine to me. Would you then use
>>
>> :lexical nil
>
> Sure. However, Babel uses "yes" and "no" as booleans so we also need to
> support these. nil and t are fine too, obviously.
>
> You would need to define a new defconst
> `org-babel-header-args:emacs-lisp' to specify allowed values
> for :lexical.
>
> Also, this should probably be documented somewehere.
>
>
> Regards,


--
Professor John Kitchin
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu

Re: funny emacs-lisp macro behavior in org-babel related to lexical-binding

[Thomas S. Dye]

Aloha John,

John Kitchin writes:

> I submitted a patch for this. I still am not sure I did it quite right.
> Is there a page anywhere that outlines what to do?
>
> e.g.
>
> create a branch, make changes, how to make patches, and mail them etc...
> or some other preferred method?

Yes, create a branch, make your changes, add and commit them, then run
the following command to wrap up the latest commit on your new branch of
the repository into a file which can be attached to email messages

           git format-patch -o ~/temp/ HEAD~1

after the command finished you will notice a new file in ~/temp
with a name like 0001-commit-message-stuff.patch

hth,
Tom

-- 
Thomas S. Dye
http://www.tsdye.com

Re: funny emacs-lisp macro behavior in org-babel related to lexical-binding

[Charles C. Berry]

On Sat, 16 Apr 2016, John Kitchin wrote:

> I submitted a patch for this. I still am not sure I did it quite right.
> Is there a page anywhere that outlines what to do?
>
> e.g.
>
> create a branch, make changes, how to make patches, and mail them etc...
> or some other preferred method?


http://orgmode.org/worg/org-contribute.html#patches

HTH,

Chuck

Re: funny emacs-lisp macro behavior in org-babel related to lexical-binding

[John Kitchin]

thanks, this is the page I was looking for.

Charles C. Berry writes:

> On Sat, 16 Apr 2016, John Kitchin wrote:
>
>> I submitted a patch for this. I still am not sure I did it quite right.
>> Is there a page anywhere that outlines what to do?
>>
>> e.g.
>>
>> create a branch, make changes, how to make patches, and mail them etc...
>> or some other preferred method?
>
>
> http://orgmode.org/worg/org-contribute.html#patches
>
> HTH,
>
> Chuck


--
Professor John Kitchin
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu