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From: ludo@gnu.org (Ludovic Courtès)
To: Andy Wingo <wingo@pobox.com>
Cc: guile-devel@gnu.org
Subject: Re: port-filename and path canonicalization
Date: Tue, 20 Apr 2010 18:57:07 +0200	[thread overview]
Message-ID: <87iq7mrrj0.fsf@gnu.org> (raw)
In-Reply-To: <m3ochea28t.fsf@pobox.com> (Andy Wingo's message of "Tue, 20 Apr 2010 11:42:58 +0200")

Hi,

Andy Wingo <wingo@pobox.com> writes:

> On Tue 20 Apr 2010 01:12, ludo@gnu.org (Ludovic Courtès) writes:
>
>> Andy Wingo <wingo@pobox.com> writes:
>>
>>> I recently added a global fluid, %file-port-name-canonicalization, which
>>> defaults to #f. But if it's 'absolute, the port name of a file port will
>>> be canonicalized to the absolute path; or, if it's 'relative, the port
>>> name is the canonical name of the file, relative to the %load-path, or
>>> the file name as given otherwise.
>>>
>>> The intention was to allow the user to control (port-filename P), so
>>> that the user could find e.g. the absolute path corresponding to that
>>> port at the time that it was made.
>>
>> My feeling is that ports shouldn’t have to deal with paths because
>> that’s a separate concern.  The %file-port-name-canonicalization fluid
>> seems like an inelegant hack to me.
>>
>> When applications have special requirements about paths, then it should
>> be up to the application logic to deal with that.

IOW, applications are free to do:

  (open-input-file (canonicalize-path filename))

instead of:

  (open-input-file filename)

And that’s all it takes at the application level.

> 2. I think a fluid is still necessary, because a file being
> compiled can do an `include' or `include-from-path', or even
> `open-input-file' in a macro, and all these cases you would want the
> same %file-port-name-canonicalization to take effect.

Indeed, this one is tricky.

I still think it’s application-specific, though.  How about calling the
fluid, say, %compiler-file-name-canonicalization instead?  :-)

> 3. The only correct time to do a path canonicalization is when the file
> is opened, because at another time, you might not be in the same current
> directory, so relative paths would resolve incorrectly.

Yes.

> 4. The application-level code is nastier if it has to canonicalize,
> because a relative canonicalization

What do you mean by “relative canonicalization”?

(I have Glibc’s ‘canonicalize_file_name ()’ in mind, which returns an
absolute path, so I’m confused.)

> cannot in general be passed to open-input-file. For example
>
>   (open-input-file "../../module/ice-9/boot-9.scm")
>
> is not the same as
>
>   (open-input-file "ice-9/boot-9.scm")

Agreed.  :-)

> So you'd have to do a set-port-filename! on the port, mucking up your
> code -- and how would you decide what to set? In N places you'd have to
> duplicate fport_canonicalize_filename, and you'd probably have to make
> scm_i_relativize_path public.

I failed to get the transition at “So”.  :-)

What does scm_i_relativize_path do?  (It lacks a leading comment, hint
hint.  ;-))

Thanks for taking the time to explain!

Ludo’.




  parent reply	other threads:[~2010-04-20 16:57 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-04-19 14:52 file names embedded in .go Andy Wingo
2010-04-19 21:46 ` Thien-Thi Nguyen
2010-04-20  0:08   ` Jose A. Ortega Ruiz
2010-04-20 11:35     ` Thien-Thi Nguyen
2010-04-20 19:15       ` Jose A. Ortega Ruiz
2010-04-21  7:45         ` Thien-Thi Nguyen
2010-04-20  9:45   ` Andy Wingo
2010-04-20 10:34     ` Thien-Thi Nguyen
2010-04-19 23:12 ` port-filename and path canonicalization Ludovic Courtès
2010-04-20  9:42   ` Andy Wingo
2010-04-20 11:15     ` Thien-Thi Nguyen
2010-04-21  8:49       ` Ludovic Courtès
2010-04-21 19:16         ` Thien-Thi Nguyen
2010-04-21 22:26           ` Ludovic Courtès
2010-04-22  7:42             ` Thien-Thi Nguyen
2010-04-20 16:57     ` Ludovic Courtès [this message]
2010-04-22 11:10       ` Andy Wingo
2010-04-22 12:50         ` Ludovic Courtès
2010-04-19 23:23 ` file names embedded in .go Ludovic Courtès

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