Re: [Haskell-cafe] Re: New Hackage category: Error Handling

Michael Snoyman schrieb:

On Mon, Dec 7, 2009 at 5:30 AM, Ben Franksen mailto:ben.franksen@online.de> wrote:

Michael Snoyman wrote:

> 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?

The error gets hidden instead of fixed?

Cheers Ben

You're right; bad programmers could do this. A good programmer will know to do one of two things when it gets an exception it does not know how to handle:

It is certainly not the task of a programming language or a library to parent its users. Despite an interesting idea, it will not work, since programmers will simply switch to a different language or library if they feel pushed around. There is an important reason to not simply catch an error and proceed as if it were only an exception: The error might have corrupted some data and there is no general way to recover from that. Say, after detecting an error you might want to close a file that you were working on. But since you are coping with an error, something you did not foresee, you cannot tell whether the file was already closed again or never opened. So it is better to just abort the program. The next higher level, the shell calling your program or the browser calling your plugin, might have registered what have opened and allocated and can reliably free those resources.