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

[Alister P. <gsp...@gm...>]

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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