On 21 Dec 2005, at 23:14, Alain.Picard@memetrics.com wrote:

Sven Van Caekenberghe writes:

...

Alain,

If I understand your fix correctly, you want to interpret NIL immediately as an empty array. Before, NIL was interpreted as a boolean, no ? What would be best ? In CL, this very convenient fact (false == empty list) is a problem when you want auto typing of arguments.

Ah, darn, yes, I forgot that it was pulling double duty as a boolean.

I did this without much tought, because what happened is that a test I had which used to run stopped running when I went from xml-rpc to s-xml-rpc, so I quickly discovered interpreting NIL as a symbol as the culprit. Now I'm not so sure.

Barring an "official" type mapping between lisp and XMLRPC, I guess it gets down to you to choose (and to document your choice).

I think losing NIL as a boolean is too costly a price to pay, so perhaps forcing user code to use empty arrays instead of empty lists is an acceptable price to pay.

So users would have to write code like this (s-xml-rpc:encode-rpc-call "method" ... (or foo #()) ... )

which sucks, but, if they don't like it, they can use vectors instead of lists as the data type for foo.

Other marshalling systems, e.g. CORBA, don't have these issues as they need to declare types up front as part of the method signature.

OK, well, thanks for reminding me of the true nature of the problem. Perhaps the best thing is to simply leave it as is.

OK, unless there are others with a different opinion, we will leave it at that for now, the mailing list archive will keep a reference of this issue for future reference.

Sven