Re: FunctionSignature, rev 2

I have a different idea for handling "overloaded" functions like fn:sum(). 
The spec "overloads" functions by changing their function signatures to 
have different numbers of arguments. So it is possible to have fn:sum($a) 
and fn:sum($a, $b) but fun:sum($a, $b, $c) is not specified and 
should not be allowed.

I think to properly handle this, org.exist.query.Module _should_ have the 
methods

FunctionSignature getSignatureForFunction(QName, numArgs)
and
Class getClassForFunction(QName, numArgs)

Change the semantics of FunctionSignature.isOverloaded() to signify that 
this _QName_ is overloaded, and that AbstractInternalModules should keep 
for that QName key in its Map a List of FunctionDefs (or a Map, keyed by 
the number of Arguments?), not just a FunctionDef. Have two implementing 
classes for fn:sum - one with one arg and one with two. Their functiondefs 
could look like:

FunctionDef(SumFunction1.signature, SumFunction1.class)
FunctionDef(SumFunction2.signature, SumFunction2.class)
etc.

This takes us away from adding semantics to try to deal with "optional" 
sequences as arguments, including the concept of "unlimited" sequences 
(which is there now but which I now think is not right).

What do you think?

On Thu, 23 Sep 2004, Wolfgang Meier wrote:

> I have been thinking a bit more about the changes you proposed. They point
> into the right direction:
>
> Currently, FunctionSignature.isOverloaded() indicates if a function may accept
> more arguments than those specified in the function signature. A typical
> example is fn:sum().
>
> However, there are also several functions that accept only one, optional
> argument. In this case, the optional argument should be made explicit.
>
> I thus propose that we
>
> 1) add another flag to SequenceType: isOptional. A predefined optional
> argument is then just specified in the argument list like a required
> argument.
>
> 2) rename isOverloaded to unlimitedArgs to indicate that a function may accept
> any number of arguments
>
> You can then implement the two methods isUnlimitedArguments() and
> isArgumentCountAllowed() based upon this information.
>
> Wolfgang
>
>
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