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Re: Bug in eval-string?

From: rm
Subject: Re: Bug in eval-string?
Date: Fri, 9 Aug 2002 11:35:31 +0200
User-agent: Mutt/1.3.24i

First of all, thank's for all these replies. I think my problem
stems partly from a missunderstanding of the documentation and from
a missunderstanding of the implementation (which admittedly i could
have examined myself. Sorry).

On Thu, Aug 08, 2002 at 10:27:59PM +0100, Neil Jerram wrote:
> [...]
>     rm> (let ((interaction-environment (lambda () boxx)))
>     rm>   (format #t "Meaning of life in a box is: ~A\n"
>     rm>           (eval-string "meaning-of-life")))
> This isn't Elisp!  The interaction-environment variable introduced by
> your let has nothing to do with the builtin interaction-environment,
> to which the documentation refers.

I think i (wrongly) assumend that eval-string is "syntactic sugar" 
for eval. So my reading of the documentation made me belive that 
eval-string would behave like the following (pseudo)code:

(use-modules (ice-9 syncase))

(define-syntax my-eval-string
  (syntax-rules ()
                ((my-eval-string string)
                  (with-input-from-string string (lambda () (read)))

maybe the documentation should be modified:

            "Evaluation takes place in the environment returned by the\n"
            "procedure @code{interaction-environment}.")

            "Evaluation takes place in the same environment as \n"
            "returned by the procedure @code{interaction-environment}.")

> BTW, note that the builtin interaction-environment is 
(at least at the
> moment) identical to current-module.

Ah, that information would have helped. 

> guile> (define boxx (make-module))
> guile> (set-module-kind! boxx 'directory)
> directory
> guile> (module-define! boxx 'meaning-of-life 42)
> #f
> guile> (save-module-excursion
>          (lambda ()
>            (set-current-module boxx)
>            (eval-string "meaning-of-life")))
> 42
> guile> 

Where would i find documentation on save-module-excursion?

And now for the RFC part:

Wouldn't the 'eval*' interface be clearer and more orthogonal if
eval-string would have a second, optional parameter specifying the
environment/module in which evaluation should take place. If no module
is specified the environment defaults to interaction-environment
(this guarantees backward compatibility). The modifications to 
the code are minimal, see below.


-- File: strports.c --------x--------------------------------------------

SCM_DEFINE (scm_eval_string, "eval-string", 1, 1, 0,
            (SCM string, SCM environ),
            "Evaluate @var{string} as the text representation of a Scheme\n"
            "form or forms, and return whatever value they produce.\n"
            "Evaluation takes place in the environment provided in the \n"
            "second, optional parameter @var{environ}. If none is given \n"
            "evalution will happen in the environment returned by the \n"
            "procedure @code{interaction-environment}.")
#define FUNC_NAME s_scm_eval_string

  SCM port = scm_mkstrport (SCM_INUM0, string, SCM_OPN | SCM_RDNG,

  if (SCM_UNBNDP (environ))
    environ = scm_interaction_environment ();
  return scm_c_call_with_current_module (environ,
                                         (void *)port);
#undef FUNC_NAME

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