Joerg Sonnenberger wrote:
> On Thu, Nov 22, 2007 at 12:15:47PM +0900, YAMAMOTO Takashi wrote:
>   
>>> On Thu, Nov 22, 2007 at 11:31:44AM +0900, YAMAMOTO Takashi wrote:
>>>       
>>>> how about returning the duplicate node rather than a boolean?
>>>>         
>>> I don't think that is a common use case. E.g. normally insert is used to
>>> prepare a new node and a duplicate entry is an actual error. I can't
>>> think of a good example where you want to replace the existing entry and
>>> didn't check for that earlier.
>>>
>>> Joerg
>>>       
>> i'm not suggesting to automatically replace an existing node.
>>     
>
> No, but for what other reason should it return a pointer to the existing
> node?
>
>   
Better reporting of the error? (Information about the existing node)

It is also often cheaper to insert, and modify the existing node if
present rather than query before insert, and then repeat the lookup for
the insert operation too. It's also more "atomic friendly" than query +
insert, should the tree be doing its own locking.