Re: open-read/open-write

Again, I think we need to catch all errors that are not under the
control of the programmer, so that people can write applications that
don't just crash and burn.

libc sets an error code when something bad happens. Perhaps some
functionality of this sort could be implemented (perhaps based on the
fileinfo function), so that errors can be caught. As much as I dislike
the idea of "returning error codes by side effects", it's nice to
stick to models people are used to. 

Perhaps all of this could be handled with optinal arguments to
open-xxx. Without optional args, open-xxx would work as it does now,
with t as optional argument, it would do what you are suggesting
(throw an error whenever something goes bad), with a symbol as
optional arg it would set the symbol with the error code, if
necessary.

Just some random ideas,

  -- Yann



On Tuesday 10 November 2009, Ralf Juengling wrote:
> On Tue, 10 Nov 2009, Yann LeCun wrote:
> > Yes, I object.
> >
> > For an interactive srcipt language it's nice to have a function that
> > just throws an error, but for a "real" programming language, you need
> > one that just tells you the file doesn't exist so your program can
> > take corrective actions and not crash and burn (like fopen() in C).
> 
> Ok. What bugs me is that open-read also returns '()' when a
> file does exist but it could not be opened for another reason
> (network proplems, no permission, too many files open, ...),
> and you have no clue what went wrong.
> 
> How about we let open-read return '()' when a file does not exist
> but raise an error when an existing file cannot be opened?
> 
> Ralf
> 
> > The solution is to keep the current open-write/read/append as they are
> > (changing them would break too many things), but to add another set
> > higher-level function that throws errors (although that is kind of
> > what "(reading <file> ....)" does).
> >
> > I don't have any good sugestions for name. Perhaps
> > file-open-r file-open-w file-open-a, or something.
> >
> >  -- Yann
> >
> > On Tuesday 10 November 2009, Ralf Juengling wrote:
> >> The functions 'open-read' and 'open-write' do not
> >> raise errors. The current behavior is this:
> >>
> >> "The empty list is returned when an error occurs while
> >> opening the file. .."
> >>
> >> I can see that this may be useful. But I believe the
> >> alternative behavior--open-read/write raising an error and
> >> printing an informative error message when the operation
> >> fails--is useful more often than the current behavior.
> >>
> >> Does anybody remember why the current behavior was chosen?
> >> Does anybody object if I change open-read/open-write (and
> >> open-append) in lush2 to raise errors?
> >>
> >> Ralf
> >>
> >>
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