Change the name of ArrayBoundsException in druntime

[Andrei Alexandrescu]

Robert Fraser wrote:
> Andrei Alexandrescu wrote:
>> Jarrett Billingsley wrote:
>>> On Wed, Oct 22, 2008 at 6:49 AM, Jacob Carlborg <doobnet at gmail.com> 
>>> wrote:
>>>> I think the name ArrayBoundsException should be changed to a more 
>>>> general
>>>> name like BoundsException, OutOfBoundsException or
>>>> IndexOutOfBoundsException. Then you can use the exception in every 
>>>> class
>>>> that have some sort of index operation and not just for an array/array
>>>> class.
>>>>
>>>
>>> 2nded.
>>
>> I agree. In fact I wanted to ask you all the following question. What do
>> you think about the current exception hierarchy in phobos? I think it is
>> terrible. Each module in std you open, the first piece of code to be
>> seen is the "class ThisModuleNameException" definition. In many (most?)
>> cases the module-specific exception does absolutely nothing in addition
>> to its base class. The putative reader (including me) tends to scroll 
>> non-critically over that passage without even blinking, mumbling in a 
>> trance - of course, yes, each module should define at least one 
>> exception type.
>>
>> Until one day when you stop scrolling and say, wait a minute. This all 
>> is repetition. And there are alternatives to catching by type - you 
>> can catch the base type and consult a field. And in fact I don't 
>> remember seeing code that depends on exceptions thrown from different 
>> modules having different types. There's something wrong here!
>>
>> I think most exception classes in phobos should be yanked if it's 
>> possible for their functionality (often nil) to be moved in the 
>> Exception base class. The module name should be a member. If someone 
>> needs to deal with an exception thrown from a specific module, they 
>> can always inspect the field. We don't need a huge hierarchy for that.
>>
>>
>> Andrei
> 
> Yes, you _could_ use a field... but the "catch a subclass" style is 
> already there and is supported by the language, so _why_ use a field? 
> Which of the following is easier?:
> 
> Option A:
> ---------
> try
> {
>      new Socket(30587);
> }
> catch(SocketException e)
> {
>      printf("Could not open socket\n");
> }
> 
> Option B:
> ---------
> try
> {
>     new Socket(30587);
> }
> catch(Exception e)
> {
>     if(e.type == ExceptionType.Socket)
>         printf("Could not open socket\n");
>     else
>         throw e;
> }

I think you'd be hard-pressed to justify the "if" inside the second 
example. You couldn't create a Socket, period. It doesn't matter where 
exactly the exception was generated from.

That's one thing about large exception hierarchies: everybody can come 
with cute examples on how they could be useful. As soon as the rubber 
hits the road, however, differentiating exceptions by type becomes useless.


Andrei