Re: new function

[Damien Mattei <damien.mattei@gmail.com>]

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yes i'm using GNU Guile 3.0.7,
https://www.gnu.org/software/guile/docs/master/guile.html/Syntax-Transformer-Helpers.html

i have tested a lot , even define-once again and i choose to use to
assignment operators and portable code because the non-portable function do
not bring more, finally it was not a bad idea to ask for a new function
because we can do it with the actual toolbox...
Damien

On Thu, Sep 23, 2021 at 10:48 PM Taylan Kammer <taylan.kammer@gmail.com>
wrote:

> Responding to myself:
>
> On 23.09.2021 22:27, Taylan Kammer wrote:
>
> > 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?
>
> Worked when I imported (system syntax internal).
>
> > Either way, I suspect that the following will not work with your macro:
> >
> >   (let ()
> >     (let ()
> >       (<$ x 1))
> >     (display x)
> >     (newline))
>
> Indeed it doesn't work, though for a different reason:
>
>   While compiling expression:
>   Syntax error:
>   unknown file:43:8: body should end with an expression in form (let ()
> (<$ x 1))
>
> That's because indeed the inner let expands into:
>
>   (let ()
>     (define x 1))
>
> And there has to be at least one expression after the define.  So I tried:
>
>   (let ()
>     (let ()
>       (<$ x 1)
>       (newline))
>     (display x)
>     (newline))
>
> And as I expected, it says 'x' is unbound:
>
>   ;;; <stdin>:44:45: warning: possibly unbound variable `x'
>   <$ : global scope : x
>
>   ice-9/boot-9.scm:1685:16: In procedure raise-exception:
>   Unbound variable: x
>
> The only way it will work is if you never use nested scopes, but that will
> lead to very strange Scheme code, and there will probably be many cases
> where you accidentally use a nested scope without immediately noticing it.
>
> Note also that definitions aren't allowed everywhere.  Consider this:
>
>   (let ()
>     (if 'whatever
>         (<$ x 1)
>         (<$ x 2))
>     (display x)
>     (newline))
>
> It leads to:
>
>   While compiling expression:
>   Syntax error:
>   unknown file:49:17: definition in expression context, where definitions
> are not allowed, in form (define x 1)
>
> Because the arms of 'if' aren't allowed to be definitions.
>
> --
> Taylan
>

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