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Re: [xsl] How do I pass the mode as a string?

2020-03-03 09:37:51
Thanks all for the explanations.  I'll look at the alternatives.
If this was C++, which is what I use most of the time (XSL is infrequent, just 
when I want to manipulate some XML) I would use some kind of polymorphism to 
achieve this.  I'd define a couple of one-line functions with the different 
variables, or calls, and pass the appropriate one to the outer function so they 
could be run on its results (somewhat garbled, abbreviated explanation, sorry). 
 I'm not aware of anything in XSL that looks like polymorphism, but I would be 
interested to know if there was a construct that might be similar, or usable 
for cases like this one.
Granted I can't construct variable names dynamically, but I can have a number 
of variables existing simultaneously and select one and pass it around by 
address if I need to.  I don't see an analogous construct in XSL, except to use 
choose/when to select a line of code based on an actual variable.

I could send my examples if that would be best, but I think that would provide 
a lot of unnecessary code just to show a small bit of context.
What I am actually trying to do is to get a number of XML files processed.  The 
files are in similar folders, called 'input' and 'output'.  The files' names 
follow a couple of name patterns, acq_(\d{4}) and out_(\d{4}). There is 
identical code to scan through the folders and identify the files I want to 
process (and extract the numbers from the filenames).  They are then passed to 
apply-templates with the different modes as mentioned.
So the file scanning, while not especially complicated, is not entirely trivial 
and I'd like to have it written just once.  And then, because the contents of 
the files differs in structure, they are handled by different templates, with 
different modes.

[Blue line]
Richard Kerry
BNCS Engineer, SI SOL Telco & Media Vertical Practice
M: +44 (0)7812 325518
2nd Floor, MidCity Place, 71 High Holborn, London, WC1V 6EA

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From: Michael Kay mike(_at_)saxonica(_dot_)com 
Sent: 03 March 2020 11:48
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com 
Subject: Re: [xsl] How do I pass the mode as a string?

Section §6.6.2 in the XSLT 3.0 spec states:

 element also has an optional mode attribute. The value of this attribute must 
be one of the following:

 which is expanded as described in 5.1.1 Qualified 
 to define the name of a mode
the token #default, to indicate that the default mode for the stylesheet 
 is to be used
the token #unnamed, to indicate that the unnamed 
 is to be used
the token #current, to indicate that the current 
 is to be used

It does not allow an expression, and it does not allow an attribute value 

It's similar to trying to refer to a variable by name: you can't construct 
variable names dynamically either, however much you feel it would make your 
life easier.

You haven't described your problem so it's difficult to suggest a different 
approach to solving it. Higher-order functions might be the right way.

Michael Kay
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