Re: GError

[Andreas Rottmann <a.rottmann@gmx.at>]

Andy Wingo <wingo@pobox.com> writes:

> Hi Kevin,
>
> On Mon, 26 May 2003, Kevin Ryde wrote:
>
>> Andy Wingo <wingo@pobox.com> writes:
>> >
>> > With regards to GError, I think the solution you propose is too much
>> > like C programming.
>> 
>> Oh, well, if it's nice and close then at least people familiar with
>> the C style will find the guile interface comfortingly similar.  Or
>> vice versa even.
>
> I'm not sure that an identical function mapping is really a goal. I am
> programming in scheme because I prefer it to C. In making these
> bindings, the goal has been to make the functionality of the gnome APIs
> available from scheme, not strict API transliteration. I don't think
> throwing exceptions will bother anyone who chooses scheme over C.
>
> A quick search through gnome/defs shows the following occurences of GError:
>
>  * Gdk: 7 uses, all regarding file i/o (pixbuf loading and saving,
>    mostly)
>  * Pango: 1 use, pango_parse_markup
>  * GConf: a boatload of uses, for a boatload of reasons: permissions,
>    client-server communication, etc etc
>  * applets: 1 use, setting something gconf-related
>  * libgnome: 4 uses, regarding failure to display help or uris
>  * glib: only appears in g_error_*
     ^^^^^^^
Not really true; there are quite a bunch of uses in glib:

~% grep GError /usr/include/glib-2.0/glib/*.h | wc -l
     68

> These are the sorts of things exceptions are made for. Furthermore,
> exposing GError to the programmer leads to nastiness on the scheme side
> of things.
>
> You could implement exceptions by adding 'c-only to the typespec and
> extending g-wrap to ignore, from the scheme side, parameters with
> 'c-only in their typespecs. The scm->c and c->scm ccodegens would still
> be run, however, allowing the error to be initialized and checked.
>
I agree that throwing exceptions instead of using GError is probably
the way to go; especially if you take this into account (from the GLib
manual):

,----
| GLib provides a standard method of reporting errors from a called
| function to the calling code. (This is the same problem solved by
| exceptions in other languages.)
`----

Regards, Andy
-- 
Andreas Rottmann         | Rotty@ICQ      | 118634484@ICQ | a.rottmann@gmx.at
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