On 2 mars 06, at 11:12, Markus Gaelli wrote:

> Hi Stef,
>
> let's have a look a the following example:
>
> Intervall >> remove: anElement
> 	self error: 'elements cannot be removed from an Interval'
>
> What do you mean with "trapped more specifically"?

Not for this one
	but
		IndexNotFoundError
		KeyNotFoundError
		SubscriptOutOfBoundsError

> I would claim that almost all (happy for any counter example) uses  
> of "self error:" are indicating that some (maybe implicit)  
> precondition fails.
> Being radical I would say in above situation the precondition just  
> fails always, meaning that this method would never make sense to be  
> called on Intervals.

But I'm not talking about that in particular.

Dictionary>>at: key
	"Answer the value associated with the key."

	^ self at: key ifAbsent: [self errorKeyNotFound]

errorKeyNotFound

	self error: 'key not found'

errorValueNotFound

	self error: 'value not found'



> Using traits we shouldn't need the strange idiom to overwrite  
> template or other superclass methods, that do not work in special  
> subclasses, any more.
> (It would be really tedious to enumerate all methods on all classes  
> which do not work... ;-)

Sure but this was not my point.

> If the error string is telling me why the precondition fails, good.  
> Why would I want to bother with different kinds of exceptions here?
>
> By the way, I call a test, which tests the failing of a  
> precondition, "pessimistic method example", but I am still open for  
> a better name.
> People did not like the name "counter example" or "negative  
> example", though I still would prefer one of these names and I am  
> about to rename...
>
> Cheers,
>
> Markus
>
> On Mar 1, 2006, at 10:29 PM, stéphane ducasse wrote:
>
>> Hi all
>>
>> I asked students of my lecture to write SUnit tests for some  
>> collections and I noticed that in Squeak
>> the collection library do not use specific exception but instead  
>> use error:.
>> The consequence is that it can be tedious to capture only specific  
>> error. I was wondering what is the
>> general feeling about this state. In VW they have various  
>> exception that can be trapped more specifically.
>>
>> Stef
>>
>
>
>