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"M. David Peterson" <m.david.x2x2x@gmail.com> wrote in message
f8da4eba0412301913514c47ae@mail.gmail.com">news:f8da4eba0412301913514c47ae@mail.gmail.com...
> "My own proposal was for special XSLT error templates that could
> "match" or trigger on error conditions, assuming a very simple XML
> vocab for XSLT error communication in the
> first place."
>
> Oooohhhh.... I totally love that idea!!! Basically like built-in
> templates that exist in the 1.0 definition... basic output and easily
> overidable if desired as such.
>
> Dimitre, can you think of a way to do this with FXSL, especially with
> XSLT 2.0 and everything being a sequence of nodes it seems that a
> certain condition could easily insert, for example, <error id="123"/>
> into the output and further apply-templates to all error elements
> before finishing each process contained within a template?
Yes, this can be done, what is only needed is implementing support for
higher order functions (HOF) and for computations (Monads).
One has to realize that error raising/handling in a functional language is
essentially nondeterministic and much more challenging as such. XPath 1.0
compatibility would also be very problematic, as there's almost no such
thing as raising an error in XPath 1.0.
More on implementing exceptions in a functional language can be found in the
classic work of Simon-Peyton Jones "Tackling the awkward squad: monadic
input/output, concurrency, exceptions, and foreign-language calls in
Haskell", at
http://research.microsoft.com/Users/simonpj/papers/marktoberdorf/
While I actually made some successful experiments 1 1/2 years ago, it seems
too early to expect these in XSLT. My predictions (which are typically
optimistic) are for HOF support in XPath/XSLT 3.0 and try/catch-type error
handling in XPath/XSLT 4.0.
The WG has done a good job and made the reasonable decision not to put the
cart in front of the horse.
Cheers,
Dimitre.
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