array slice syntax

Stefan Gössner stefan at goessner.net
Thu Aug 16 23:41:51 PDT 2007


thanks for the clarification
--
stefan

Brendan Eich wrote:
> On Aug 16, 2007, at 10:42 AM, Lars T Hansen wrote:
> 
>> On 8/16/07, Stefan Gössner <stefan at goessner.net> wrote:
>>> Hello,
>>> here are my first questions after following the list quite a while.
>>>
>>> 1. I really like the array slice syntax [start:end:step] described in
>>> http://developer.mozilla.org/es4/proposals/slice_syntax.html
>>>
>>> The description seems to miss the case, where 'start' is greater  
>>> than 'end'.
>>>
>>> a[5:2]
>>>
>>> Will
>>> (a) 'step' be implicitely set to -1 ?
>>> (b) an empty array come as result ?
>>> (c) an error occur ?
>> The description seems to be clear here, the result should be an  
>> empty array.
> 
> Same as for Python:
> 
>  >>> s = [1,2,3]
>  >>> s[2:1]
> []
> 
>>> 2. The descendant operator '..' is mentioned only in the tutorial
>>> introduction.
>>> http://developer.mozilla.org/es4/spec/ 
>>> chapter_1_tutorial_introduction.html
>>> I could not find it mentioned elsewhere.
>>>
>>> Is it also considered to work with array notation as in:
>>>
>>> y..[0]   // access the first element of all arrays of 'y' and it's
>>> descendants.
>> I don't think so.  The descendant operator is for E4X (ECMAScript for
>> XML, ECMA-357) and has not been discussed in other contexts.  E4X is
>> not included in ECMAScript 4 at this stage.
> 
> We are reserving E4X syntax but not requiring it to be supported.
> 
> The .. operator bugs me because it implicitly quotes its right  
> operand (as . does), so you could not use it as Perl and other  
> languages do for range operator. If it were a dyadic operator that  
> did not quote either operand, than it could be overridden by the  
> operators proposal (or an operators proposal, at any rate ;-) and  
> made to work for range (integer literal or value on left) as well as  
> for E4X (XML on left).
> 
> Generalizing query, matching, and filtering from E4X to the whole  
> language, cleaning up the "un-JavaScript-y" aspects of E4X, making  
> use of practical research such as JMatch [1], all will have to wait  
> for a future Edition. But we certainly can discuss ideas here. Please  
> feel free to do so.
> 
> /be
> 
> [1] http://www.cs.cornell.edu/Projects/jmatch/
> _______________________________________________
> Es4-discuss mailing list
> Es4-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es4-discuss
> 




More information about the Es4-discuss mailing list