Re: [Caml-list] exception handling questions

[Eric Stokes <eric.stokes@csun.edu>]

On Nov 6, 2003, at 1:50 AM, Dustin Sallings wrote:

>
> On Nov 6, 2003, at 1:02, Richard Jones wrote:
>
>>> 	One thing that really seems to be missing from exception handling is
>>> the ability to print a stack trace from an exception.  I realize
>>> there's a flag on the ocamlrun to print stacks for uncaught 
>>> exceptions,
>>> but that's not exactly what I'm looking for.  I'd like to be able to
>>> catch and exception, log it, and continue.
>>>
>>> 	Similarly, is there a way to print an exception at least like the
>>> toplevel does?  I can catch any type of exception with the 
>>> appropriate
>>> pattern, but I don't see how I can report it without expecting it.
>>
>> And while we're at it, printing out a full stack trace with function
>> names and parameters.
>
> 	Yes, that would be nice, but I'm trying to not ask for too much.  :)  
> As it is, I've got a function that can fail when processing large 
> amounts of data and it's OK to lose one as long as I know why.  Right 
> now, the only way to know why is to rethrow:
>
> let should_process fn =
>     try
>         (ends_with fn ".") && (is_new_enough fn) && (not (is_gzip fn))
>     with x ->
>         print_endline("Unknown error determining whether to process " 
> ^ fn);
>         raise x
> ;;
>

What about doing this.

let rec should_process fn =
     try
         (ends_with fn ".") && (is_new_enough fn) && (not (is_gzip fn))
     with x ->
         print_endline("Unknown error determining whether to process " ^ 
fn);
         should_process fn
;;

You may need to maintain a bit more state in various places, but it 
could work
the way you want.

> 	Example output:
>
> Unknown error determining whether to process /tmp/x/passwd.
> Fatal error: exception Sys_error("/tmp/x/passwd.: Permission denied")
>
> 	I'd be plenty happy to print out that message and continue, but in 
> the meantime, I've gotta have it abort.
>
> -- 
> Dustin Sallings
>
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