Re: Extension candidates

Florent Georges wrote:
> John Snelson wrote:
> 
>   Hi John,
> 
>> http://snelson.org.uk/~jpcs/higher-order-functions.html
> 
>> As Michael says, it might be appropriate for EXSLT to attempt
>> something simpler than this proposal - but it will hopefully give
>> people something to think about.
> 
>   It is indeed very interesting!
> 
>   First two little questions (a bit OT here, sorry): 1/ it seems it
> is not possible to create a function item from a dynamic QName, is
> it on purpose? (I guess so),

I hadn't thought about making it dynamic. The problem with doing so 
would mainly be that the implementation could know very little about the 
type of a function whose name was not known at compile time. I guess I'd 
need to see a use case for being able to do that.

> and 2/ what's the difference between
> both following item types (from the type hierarchy in "1 Function
> Items")?
> 
>     function()

This means any function item (any arity, arg type and result type).

>     function() as item()*

This means a function item that takes no arguments and returns a 
sequence of items.

>   About possible simplifications, I think the most obvious are
> changes to the grammar.  Some can be changed to extra extension
> functions (for example a function that returns a function item
> instead of literals,) other are more touchy (like inline
> functions.)  Some concrete proposals:
> 
>   - do not define the extension to ItemType, and do not define the
>     exact type of a function item (can be defined as it were a new
>     type of items, but no assumption nor test can be made about the
>     real type of such items);
> 
>   - define a function to create function items instead of literals
>     (should the name of the function by a real QName item, or a
>     QName literal?);
> 
>   - do not define inline functions (at least in a first time);
> 
>   - define a function ex:call() for 1.3 Dynamic Function
>     Invocation.

That sounds reasonable.

John

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