Re: new function

[Taylan Kammer]

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