RE: [xsl] Re: A proposal:xsl:result-document asynchronous attribute

[Dimitre Novatchev <dnovatchev@xxxxxxxxx>]

> > For the time being such support will be provided by the FXSL 
> > monadic implementation.
> > 
> > Before publishing the initial implementation I'm trying to 
> > collect a number of good-use examples, like maintaining 
> > state, update-in-place Arrays, IO from external files, 
> > synchronous exceptions.
> 
> I've seen some examples recently where initializing a Java object
> requires two calls: a constructor and an initialization.
> 
> <xsl:variable name="x" select="java:object.new()"/>
> <xsl:do select="setProperty($x,17)"/>
> <xsl:value-of select="$x"/>
> 
> Somehow the second instruction has to be forced to happen before the
> third. The way I fudge it at present is to write the "xsl:do" as
> "xsl:value-of", but I've had to tweak the optimizer so it doesn't
> skip
> the instruction because it recognizes statically that the result is
> always empty.

Thank you Mike, for the good example.

BTW, what is xsl:do? I couldn't find it in the current WD spec.

> 
> Generally the Saxon optimizer has now got to the level where external
> functions with side-effects are becoming very troublesome. I've been
> thinking of introducing some kind of construct to force sequential,
> unoptimized execution of a sequence of instructions. (And for the
> time
> being, I've overloaded the attribute saxon:assignable="yes" to
> achieve
> this effect).

I've heard horror stories of an XSLT processor completely discarding an
xsl:variable and then re-evaluating it. In such case even a monadic
implementation will not help -- there must be something to tell the
processor not to discard and "recreate" a certain variable, because
evaluating its value causes a side-effect.

In the absence of the ability to express that a variable is of type

IO a

this would be the way to say it.





 

=====
Cheers,

Dimitre Novatchev.
http://fxsl.sourceforge.net/ -- the home of FXSL

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