Re: [Tinyscheme-issues] problem with (load "file.scm")

[Jonathan S. S. <sh...@er...>]

On Mon, 2008-01-21 at 22:40 -0500, Tom Breton (Tehom) wrote:
> > However, note that there is an inherent ambiguity about what LOAD means
> > when it is called from any place that is not top level. Specifically:
> > the LOAD will internally execute a REPL loop, and it is not obvious what
> > environment that REPL loop runs in? In particular, does it's environment
> > (if not specified explicitly as an argument to LOAD) include any
> > non-globals that were bound in the procedure calling LOAD?
> >
> > I don't know the answer, and the standard does not take a position.
> 
> I don't know, but what makes sense to me is to use the environment load
> was called in.

Actually, I think that this is exactly the wrong thing to do. In the
absence of specification, LOAD should be called with the TOP-LEVEL
environment, not the current lexical environment.

Rationale:

The in-procedure case introduces misleading complexity. Calling load
form a procedure is generally a mistake. The cases we want to consider
are of the form:

  (load "a.scm")
  (load "b.scm") ; must be able to reference results of a.scm
  (if (test) (load "c.scm) #f)

If you see a load within a procedure of the form

  (load "x.scm" (current-environment))

well, then, the user said "current lexical env" and fuck 'em if they
can't take a joke. But in the absence of an argument I claim that the
local ENV must NOT be captured "by magic". If you accept this, then the
two credible rewritings are:

  (load "x.scm") => (load "x.scm" (r5rs-environment))
  (load "x.scm") => (load "x.scm" (top-level-environment))

I claim that the second is the correct interpretation, because otherwise
we must conclude that

  (load "a.scm") (load "b.scm") =>
    (load "a.scm" (r5rs-environment))
    (load "b.scm" (r5rs-environment))

and it would follow generally that later loads cannot use the results of
earlier loads -- which is obviously not what we intend.


shap