The Right Approach to Exceptions

[foobar]

On Monday, 20 February 2012 at 15:50:08 UTC, Andrei Alexandrescu 
wrote:
> On 2/20/12 3:01 AM, foobar wrote:
>> On Monday, 20 February 2012 at 07:10:39 UTC, Andrei 
>> Alexandrescu
>> wrote:
>>> On 2/20/12 12:44 AM, foobar wrote:
>>>> I just died a little reading this. Are you suggesting that in
>>>> order to handle IO exceptions I need to: try { 
>>>> ...whatever... }
>>>> catch (PackageException!"std.io") {...} } catch
>>>> (PackageException!"tango.io") {...} } catch
>>>> (PackageException!"otherLib.io") {...} ...
>>>>
>>>> What the hell is wrong with just using an IOException?
>>>
>>> There's nothing wrong, but there's a possible 
>>> misunderstanding. If
>>> tango.io and otherLib.io cooperate with std, then they'd 
>>> originate
>>> exceptions in std.io (as opposed to their own). Do note that 
>>> the
>>> issue is exactly the same if libraries use IOException - they 
>>> all
>>> must agree on using the same nomenclature, whether it's called
>>> PackageException!"std.io" or IOException.
>>>
>>
>> The above is patently wrong. Are you suggesting that tango.io 
>> and
>> otherLib.io need to depend on Phobos IO?? If so, that removes 
>> the
>> benefits of using 3rd party libraries. If that's not your 
>> intention
>> (and I really hope it isn't!) than IOException must be defined 
>> in a
>> *separate* module that tango can depend on.
>
> Actually that just shuffles the matter around. Any setup does 
> demand
> that some library (in this case most probably the standard 
> library) will
> be a dependency knot because it defines the hierarchy that 
> others should
> use.

Not accurate. A 3rd party library that want to be compatible will 
no doubt depend on the standard library's _exception hierarchy_ 
but that does *not* mean it should depend on the parallel 
functionality in the standard library. Per our example with IO, 
if I use tango.io I certainly do not want my application code to 
include redundantly both std.io and tango.io. I wanted to use 
tango.io as an *alternative* to std.io.

>
>> [Meta] side-note: It's extremely irritating when you demand 
>> utmost
>> pedantic reasoning from others while you often answer without
>> providing such pedantic reasoning yourself or worse answer 
>> with a
>> single word posts. That shows a complete lack of respect for 
>> others.
>> You seem to be of high regard for yourself which is not 
>> justified at
>> all given this attitude.
>
> When giving brief answers I was trying to maximize throughput 
> in a couple of cases when the meaning was obvious from the 
> context. Otherwise I do my best to elaborate my points. But I 
> see how that can be irritating, I won't continue it.
>
>

Thank you.

> Andrei