Spec#, nullables and more

[Rainer Deyke]

On 11/6/2010 02:47, Walter Bright wrote:
> Rainer Deyke wrote:
>> On 11/5/2010 17:41, Walter Bright wrote:
>>> In other words, I create an array that I mean to fill in later, because
>>> I don't have meaningful data for it in advance.
>>
>> That's a faulty idiom.  A data structure that exists but contains no
>> valid data is a bug waiting to happen - no, it /is/ a bug, even if it
>> does not yet manifest as incorrect observable behavior.  (Or at best,
>> it's an unsafe optimization technique that should be wrapped up in an
>> encapsulating function.)
> 
> An example would be the bucket array for a hash table. It starts out
> initially empty, and values get added to it. I have a hard time agreeing
> that such a ubiquitous and useful data structure is a bad idiom.

Empty is a valid value for a hash table, so that's a completely
different situation.  Obviously the bucket array would not use a
non-nullable type, and less obviously the bucket array should be
explicitly initialized to nulls at creation time.


-- 
Rainer Deyke - rainerd at eldwood.com