Re: add-relative-load-path ?

[Neil Jerram]

Andy Wingo <address@hidden> writes:

> Hi Neil,
>
> On Sat 14 Jan 2012 22:48, Neil Jerram <address@hidden> writes:
>
>> Andy Wingo <address@hidden> writes:
>>
>> Of the possibilities above, I think I prefer
>>
>>>   (add-to-load-path (dirname (current-source-filename)))
>
> Done.  Actually I called it "current-filename", so it would be:
>
>   (add-to-load-path (dirname (current-filename)))
>
> Feedback is very welcome -- especially timely feedback; it would be nice
> to release on Monday or so.  I'm attaching the patch (already committed)
> to make it easy for you :)

Thanks!

The patch works for me, although there are a couple of points that still
make it a bit fiddly to use in practice.  It might be possible to
improve the first of those points, but I don't think anything can be
done about the second.

Thing 1 is that (current-filename) can return a relative filename, or a
filename with a "./" in its middle:

1.1: With a script called "affiche", with "#! /usr/bin/guile -s" and
which I invoke from the shell as "./affiche", (current-filename) gives
"/home/neil/q/SW/ossaulib/scripts/./affiche".  So if I do (dirname
(dirname (current-filename)), intending to get the parent directory
"/home/neil/q/SW/ossaulib", I actually get
"/home/neil/q/SW/ossaulib/scripts".

1.2: If I encapsulate the load-path logic in a separate file called
"setup-load-path.scm", and take advantage of the fact that (include
"setup-load-path.scm") will find that file in the same directory as
"affiche", (current-filename) gives just "setup-load-path.scm", and
(dirname ...) on that won't give a useful result.

Both problems are solved by adding in a canonicalize-path call.  Would
there be any downside from putting that inside current-filename, so that
current-filename always returns a canonical file name?

Alternatively, I think the use of canonicalize-path should be added into
the example in the manual.

Thing 2 is that it remains slightly inelegant to cater for both 1.8 and
2.0.  I think the minimal complete solution is to write

(cond-expand (guile-2 (include "setup-load-path.scm"))
             (else (load "setup-load-path.scm")))

at top level in every uninstalled script, and then something like

(cond-expand (guile-2
              (add-to-load-path
               (dirname
                (dirname
                 (canonicalize-path (current-filename))))))
             (else
              ;; Less elegant code for 1.8...
              (let* ((bindir (dirname (car (command-line))))
                     (absdir (cond ((string=? bindir ".")
                                    (getcwd))
                                   ((string-match "^/" bindir)
                                    bindir)
                                   (else
                                    (in-vicinity (getcwd) bindir)))))
                (set! %load-path (cons (in-vicinity absdir "..")
                                       %load-path)))))

in setup-load-path.scm.

But without a time machine I don't think anything can be done to make
either of those fragments more concise.

I also had just one comment on the doc:

> @@ -814,9 +780,9 @@ change occurs at the right time.
>  @defvar %load-hook
>  A procedure to be called @code{(%load-hook @var{filename})} whenever a
>  file is loaded, or @code{#f} for no such call.  @code{%load-hook} is
> -used by all of the above loading functions (@code{load},
> address@hidden, @code{primitive-load} and
> address@hidden).
> +used by all of the loading functions (@code{load} and
> address@hidden, and @code{load-path} and
> address@hidden documented in the next section).

[...]

> address@hidden {Scheme Procedure} load-from-path filename

Is it 'load-path' or 'load-from-path'?

Regards,
        Neil