Subj : Re: E4X: result of parent() method call on XMLList
To   : Martin.Honnen
From : Brendan Eich
Date : Sat Apr 16 2005 05:22 pm

Martin Honnen wrote:
> 
> 
> Martin Honnen wrote:
> 
>> The E4X specification says that undefined should be returned on 
>> calling parent() on an empty XMLList but Spidermonkey returns null.
>> The errata (https://bugzilla.mozilla.org/attachment.cgi?id=169406) 
>> already mentions the discrepancy.
>> Is there any decision by now what should be returned, null or undefined?
> 
> 
> Spidermonkey behaves differently than I state above, for an empty 
> XMLList it indeed returns undefined but for the following XMLList it 
> returns null while the spec would mandate undefined too:
> 
> js> var godList = <><god>Kibo</god><god>Xibo</god></>;
> js> print(godList.parent())
> null
> 
> Rhino returns undefined.


Sorry, my last reply was typed as I saw only your first post 
(Thunderbird really should scroll all new messages into view, if they 
fit -- anyone know of a bug on that?).

Anyway, why do you say the spec mandates undefined?  Here is the 
XMLList.prototype.parent algorithm in full:

1. If l.[[Length]] = 0, return undefined
2. Let parent = l[0].[[Parent]]
3. For i = 1 to l.[[Length]]-1, if l[i].[[Parent]] is not equal to 
parent, return undefined
4. Return parent

Note that both <god> elements have null as parent, so step 4 will return 
parent, which is l[0].[[Parent]] or null.

Somone please file a Rhino bug.

/be

.