[xsl] Re: mapping (Was: Re: Re: . in for)

[Dimitre Novatchev <dnovatchev at yahoo dot com>]

Joerg Pietschmann <joerg dot pietschmann at zkb dot ch> wrote: 

[snip]

> This means you want lambda expressions.
> 
> >  - define a map expression (rather than a map() function)
> 
> Note that in you proposal of a mapping operator
>   $coordinates -> (. * 2)
> the second operand actually *is* already a lambda expression. Hint:
> the . is not bound to the value of the context node as it would
> have been in ordinary expressions.
> We can argue about inventing an XPath function xf:lambda() for this
> purpose, with all the consequences. I'd probably like it to have one,
> but i let it to Dmitre to make up the full proposal... :-)

I already noticed that Jeni's "mapping operator" is in fact lambda expression.

However, why make a special proposal for lambda expressions. The surprisingly
energetic response indicates that what people want (and nobody stood against this)
is support for higher-order functions in XPath 2.0. Having higher-order functions in
place, anonymous functions (lambda expressions) will naturally come as an added
benefit or just as a convenient shorthand. 

Cheers,
Dimitre.


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