Re: [Exist-development] [Exist-open] type-specific parameters in overloaded functions

[Dave F. <dav...@gm...>]

Aw, son of a gun!

So, with the item() parameter, I can use typeswitch to delegate to various
sub-functions as I see fit. Basically, what I need is a base function that
handles the grunt work, which I already have. With an ID (integer) parameter
I can construct a string that points to an XML file via an XMLDB URL.
Allister's suggestion makes the most sense since I can construct a sort of
"degenerate" function that all variances will call upon.

As such, I have my solution. Tomorrow will be glorious!

On Sat, Apr 16, 2011 at 12:13 AM, Alister Pillow <gsp...@gm...>wrote:

> Hi Dave,
> Yes - it's a language issue:
> [Definition: Function signatures. This component defines the set of
> functions that are available to be called from within an expression. Each
> function is uniquely identified by its expanded QName and its arity (number
> of parameters).]
>
> So Dimitry's suggestion (to edit the source) is possible, but it would be
> breaking the rules.
>
> An alternative is to define one function that takes any parameter, and use
> the typeswitch expression to deal with them.
> declare function local:my-function ($param as item()) {
>    typeswitch($param)
>       case $a as xs:integer return $a + 1
>       case $a as xs:string return upper-case($a)
>       default return "unknown"
> };
>
> I hope that is useful.
>
> Alister.
>
>
> On 16/04/2011, at 2:03 PM, Dave Finton wrote:
>
> > I'd like to define a function (or two) where they can be called one of
> the following ways:
> >
> > dave-module:my-function ($my-string as xs:string)
> > dave-module:my-function ($my-integer as xs:integer)
> >
> > The problem is that eXist (or perhaps it's the XQuery language in
> general) doesn't like this, as it seems unless I define functions based on
> the *number* of parameters as opposed to the *type*, I get an error. No
> matter how I try, the interpreter seems to want one over the other. My
> question: Is there a way to not have to do any obvious workarounds to get
> this to work? Right now all I can do is to define the functions as follows,
> which does work:
> >
> > dave-module:my-function-s ($my-string as xs:string)
> > dave-module:my-function ($my-integer as xs:integer)
> >
> > (note the "-s" at the end of the function name to denote the fact that it
> is expecting a string)
> >
> > I'm using eXist 1.5 trunk (I forget the revision number off the top of my
> head). My apologies if this is a neophyte question, but after a day of
> rummaging through the documentation, I'm kind of at a loss.
> > --
> > David Finton
> >
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-- 
David Finton