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Re: cond clause does not allow definitions


From: Damien Mattei
Subject: Re: cond clause does not allow definitions
Date: Thu, 23 May 2024 00:09:53 +0200

in the version below it seems that else in cond with definition works alone
but not when there is other conditions before:

GNU Guile 3.0.8.99-f3ea8
Copyright (C) 1995-2022 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> (cond (else (define x 7) x))
$1 = 7
scheme@(guile-user)> (cond (#f 'never) (else (define x 7) x))
While compiling expression:
Syntax error:
unknown file:2:24: definition in expression context, where definitions are
not allowed, in form (define x 7)

i understand that because  in my code, that i can not write all here,  i
had  to change:
#`(cond  (#,test (let ()
     #,@L-then))
   (else
      #,@L-else)))

#`(cond  (#,test (let ()
     #,@L-then))
   (else
    (let ()
      #,@L-else))))

add a (let ()  in the else of cond too to encapsulate the possible
definitions in #,@L-else

now i understand that and it is late here...
good night

On Wed, May 22, 2024 at 11:08 PM Pierpaolo Bernardi <olopierpa@gmail.com>
wrote:

> On Wed, May 22, 2024 at 10:08 PM Jeronimo Pellegrini <j_p@aleph0.info>
> wrote:
>
> > A: (cond (#t (define x 7) x))
> > B: (cond (else (define x 7) x))
> >
> > | system      | A     | B     |
> > |-------------|-------|-------|
> > | Bigloo      | 7     | 7     |
> > | Biwa        | 7     | 7     |
> > | Chez        | error | 7     |
> > | Chibi       | error | 7     |
>
> In chez:
>
> > (cond (else (define x 7) x))
> 7
> > x
> 7
>
> which looks like a bug to me. You may check if x is defined outside of
> the cond expression in the other implementations which do not raise an
> error too?
>


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