On Dec 14, 2004, at 9:42 AM, Stéphane Rollandin wrote:

> Brian Rice wrote:
>> Slate uses a language extension called optional keywords for this, 
>> where any message-send may pass along a number of &-prefixed keywords 
>> (read & as "with") and then ordinary expressions to override any 
>> defaults for auxiliary inputs. Each method can then define auxiliary 
>> inputs which it responds to and which can have default expressions to 
>> initialize them.
>
> looks like lisp syntax...

Well, yeah, Slate was initially implemented as a dynamic compiler to/on 
Common Lisp by a couple of long-time Lisp (and Squeak) users, so it 
just seemed natural (to us). Also, we made the logical binary messages 
/\ and \/ which freed up & and eliminated | ambiguity, so it fit to 
re-use &. It actually looks like "messageSend &foo: fooValue &bar: 
barValue" to be clear.

>> The auxiliary keywords can be passed in any order or combination. One 
>> tiny annoyance is that adding keywords to any message-send raises its 
>> arity to keyword-level instead of just binary or unary.
>> It's an idea; don't know if you'll like it. We have gradually 
>> incorporated them more and more into the libraries and it has a 
>> pleasant effect on the protocols.
>
> it could be exactly what I'm looking for. is this difficult to 
> implement in a current Squeak image ?

That's an interesting question for someone else to answer. There's some 
silly syntax kluge floating in Croquet code for C-wrapper calls that 
uses optionals that might be instructive. Then again, it might be yet 
another hack - these syntax extensions always raise grammar issues, 
which is why we've been off toying with language ideas in a 
from-scratch system.

In squeak, I usually just settle for the one-less-argument wrapper 
method which supplies the default value to the original; it's a 
reasonable emulation for keyword options <= 2, and in fact you could do 
like Avi's multi-dispatch hack and just translate code with the 
optional keywords into underlying methods which are what I describe as 
emulation.

--
Brian T. Rice
LOGOS Research and Development
http://tunes.org/~water/