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From Steve Loughran <ste...@apache.org>
Subject Re: new Task subclass
Date Tue, 27 Jul 2004 10:57:27 GMT
Phil Weighill-Smith wrote:
> XPath is a language that handles complex expressions that *can* include
> document navigation and "query" paths but also contains a lot of other
> capabilities (consider what you can do with expressions in XSLT: these
> expressions use XPath with extension functions).
> 
> My suggestion is to have Ant register extension functions with the
> *XPath* context so that they are callable from XPath; however, in my
> original message I suggested a single (standardized) "call" method that
> can be used to call any registered Ant task as a catch-all. I also
> suggested that you *might* want to invoke a target (for some reason)
> within the expression and that this could be achieved using the document
> navigation features of the XPath "language" (though what a return value
> is from a target I don't know other than "success" or "BuildException
> thrown").
> 


> Following your example we could register (again as I suggested) special
> functions for the "standard" conditionals, so the expression could look
> like:
> 
> ${cond: available("file", $myFile, "type", "file")}

1. I'd worry that you are effectively defining a new language -a 
functional one- inside ant.

2. it doesnt have to be ${}; we would be better using a new symbol like 
x{}, though again, things will  break and we will get accused of having 
the perl attitude to obscure bits of the keyboard.

3. given that my main issue with xpath, is it possible to plug in new 
axes for resolving references into the xpath engine we'd use.

4. Is there an xpath engine built in to xerces?

if we could have a new path axis, then we could have references like 
ant:://myproject/dist ; this would let us resolve using the build file 
structure, (here a targt called dist in a project called 'myproject') 
instead of using classic xpath document-centric path resolution.

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