[Xpath-ng] Proposal for definition of values/lists

[Uche Ogbuji]

> Hi Jeni,
>  
> >   Every value in XPath NG is a list or an atom. A list is a sequence
> >   of zero or more values. Atoms are of two kinds: nodes and data.
> >   Nodes are atoms that have identity whereas data are atoms that do
> >   not have identity.
> 
> What's the purpose of having two kinds of atoms? Yes, nodes have
> identity, other data types have not. But there are numerous things
> that differentiate value types, what makes the identity property
> so special?

I think this is really just a matter of editorial preference.  I could go 
either way with whether there are 2 or 4 kinds of atoms.


> >   [Issue: Should we have node sets instead of generic lists?]
> Not sure, I think no if we can retain most of the XPath 1.0 semantics.
> 
> >   [Issue: Should we allow only flattened lists rather than allowing
> >    lists to hold lists?]
> No, I think we should allow nested lists
> 
> >   [Issue: Should we allow heterogeneous lists or only allow lists
> >    whose items are all nodes, all atoms or all lists?]
> Heterogeneous

I personally wouldn't mind heterogeneous, but I think it might really queer 
things fro some implementors.


> >   [Issue: Should the string "false" cast to boolean false?]
> No, defenitely not IMO

Emphatically agreed.


> >   [Issue: Should lists be converted to strings by concatenating the
> >    string value of each value, with spaces as separators?]
> No, provide a join function for this instead

Yep.


> [Issue: Singleton lists, are they treated transparently as the value of their only item?]

Good question.  I'd say "no".  SIngleton and empty lists are still lists in 
all particulars.


-- 
Uche Ogbuji                                    Fourthought, Inc.
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