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From: Taylan Kammer <taylan.kammer@gmail.com>
To: Damien Mattei <damien.mattei@gmail.com>
Cc: Jean-Paul Roy <jean-paul.roy@unice.fr>,
	guile-devel <guile-devel@gnu.org>
Subject: Re: new function
Date: Thu, 23 Sep 2021 22:27:31 +0200	[thread overview]
Message-ID: <9c058f24-5b15-417a-17ff-10bc13fed12d@gmail.com> (raw)
In-Reply-To: <CADEOadePDXQJZgQJG1oK9Bj16EaY2zGs+OBYauj=E0sUf8Pg9g@mail.gmail.com>

On 23.09.2021 19:27, Damien Mattei wrote:
> yes i know parsing the whole code is the only portable solution, but it is slow,even on a few dozen of lines the slowing is visible ,so i can even think of that on one thousand lines...
> 
> I finally succeed in Guile with simple piece of code to make my example run with a single assignment operator <-  , here i define for variable the assignment operator <$ , <- is working with arrays too:
> 
> *Preview:*
> 
> (define-syntax <$
>   
>   (lambda (s)
>     
>     (syntax-case s ()
>       
>       ((_ var value)
>        
>        (case (syntax-local-binding #'var)
> 	 
>          ((lexical) #'(begin
> 			(display "<$ : lexical scope : ")
> 			(display (quote var))
> 			(newline)
> 			(set! var value)))
> 	 
> 	 ((displaced-lexical) #'(begin
> 				  (display "<$ : displaced-lexical scope : ")
> 				  (display (quote var))
> 				  (newline)
> 				  (set! var value)))
> 	 
>          ((global) #'(begin
> 		       (display "<$ : global scope : ")
> 		       (display (quote var))
> 		       (newline)
> 		       (define var value)))
> 	 
>          (else #'(begin
> 		   (display "<$ : unknow variable scope :")
> 		   (display (quote var))
> 		   (error "<$ : unknow variable scope : "))))))))
> 

I can't seem to find syntax-local-binding in Guile 2.2 or 3.0.  Did you
have to import some special module, or are you using another version?

Either way, I suspect that the following will not work with your macro:

  (let ()
    (let ()
      (<$ x 1))
    (display x)
    (newline))

If I understand correctly, it will expand to:

  (let ()
    (let ()
      (define x 1))
    (display x)
    (newline))

And that won't work because 'x' is only defined in the inner 'let'.

This is where we see the crucial difference between Scheme and Python:
in Python there is nothing similar to an inner 'let'.  There is only
one function-level scope.  In Scheme, there can be as many nested
scopes as you want, and an inner scope can't affect an outer one.

-- 
Taylan



  parent reply	other threads:[~2021-09-23 20:27 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-19  7:54 new function Damien Mattei
2021-09-19 14:41 ` Matt Wette
2021-09-19 14:43   ` Matt Wette
2021-09-19 21:38 ` Taylan Kammer
2021-09-21 12:26   ` Damien Mattei
2021-09-22  8:44   ` Damien Mattei
2021-09-22  9:06     ` William ML Leslie
2021-09-22  9:53       ` Damien Mattei
2021-09-22 18:51         ` Taylan Kammer
2021-09-22 21:52           ` William ML Leslie
2021-09-23  8:40             ` Damien Mattei
2021-09-23 19:03             ` Taylan Kammer
2021-09-23 17:27           ` Damien Mattei
2021-09-23 18:00             ` Maxime Devos
2021-09-23 20:27             ` Taylan Kammer [this message]
2021-09-23 20:42               ` Damien Mattei
2021-09-23 20:48               ` Taylan Kammer
2021-09-23 21:53                 ` Damien Mattei
2021-09-24  4:41                   ` Damien Mattei

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