Re: [TCLCORE] TIP #290: Registration of Custom Error Handler Scripts

[Neil M. <ne...@cs...>]

On 3 Nov 2006, at 08:44, Eckhard Lehmann wrote:
>> Just an endorsement to this... You wouldn't implement a procedure  
>> this way in practice.
> ^^^^
>
>> Why? Because you can't debug it with *any* method - it is useless  
>> here to catch the error just to rethrow it at a different place.  
>> The only good reason to catch an error and rethrow it is to do  
>> some special processing *immediately* - e.g.
>
> Ahhmm I should have seen that [using] actually *does* this kind of  
> special processing (by closing the $chan no matter if error or  
> not). My fault, the above marked was a wrong statement... sorry.
>
> But the point stays the same.

Actually, as the author of [using] and several other control  
constructs, I can say that you definitely do end up catching  
everything just to rethrow errors again. Apart from being essential  
in order to clean up resources (i.e., equivalent of a "finally"  
clause), it is also necessary if you want to catch "break" or  
"continue" exceptions. This isn't some obscure corner case: any time  
you want to [catch] anything you have to catch everything and then  
rethrow those exceptions you don't know how to deal with.

-- Neil