[Haskell-cafe] New Hackage category: Error Handling

Michael Snoyman michael at snoyman.com
Sat Dec 5 18:00:02 EST 2009

On Sun, Dec 6, 2009 at 12:55 AM, Henning Thielemann <
lemming at henning-thielemann.de> wrote:

> On Sun, 6 Dec 2009, Michael Snoyman wrote:
>  I think there are plenty of examples like web servers. A text editor with
>> plugins? I
>> don't want to lose three hours worth of work just because some plugin
>> wasn't written
>> correctly. For many classes of programs, the distinction between error and
>> exception is
>> not only blurred, it's fully irrelevant. Harping on people every time they
>> use error in
>> the "wrong" sense seems unhelpful.
>> Hope my commenting on this subject doesn't become my own form of
>> *pedantry*.
> In an earlier thread I have explained that one can consider a software
> architecture as divided into levels. What is an error in one level (text
> editor plugin, web server thread, operating system process) is an exception
> in the next higher level (text editor, web server, shell respectively). This
> doesn't reduce the importance to distinguish between errors and exceptions
> within one level. All approaches so far that I have seen in Haskell just mix
> exceptions and errors in an arbitrary way.

I think we can all appreciate why it would be a bad thing is we treat
exceptions as errors. For example, I don't want my program to crash on a
file not found.

On the other hand, what's so bad about treating errors as exceptions? If
instead of the program crashing on an array-out-of-bound or pattern-match it
throws an exception which can be caught, so what?

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