Clojure Protocols & expression problem

[Andrei Alexandrescu]

On 04/28/2010 07:38 PM, bearophile wrote:
> Andrei Alexandrescu:
>> I'm having trouble picturing the following scenario for a day in
>> life.
>
> After your experience with Loki, what do you think about double
> dispatch in external functions in D3?

Good question. Statistically, I'd say very few people are interested in 
double dispatch. I've received reams of feedback from readers. Only a 
couple inquired or mentioned the double dispatch chapter at all. This is 
a bit odd because I think Loki's offering for double dispatch is 
comprehensive. It also had a few bugs in it that went unnoticed for a 
long time, which to me suggest very few actually needed that code.

Of course that's just a data point of sorts.

If we're to discuss double dispatch, I think we should first look at 
library solutions and at ways to improve the language to allow general 
solutions to categories of problems instead of cutesies like @virtual 
function parameters.

Above all, I think at this time we should go with improving the language 
definition and the quality of the compiler. There are quite a few 
strident notes in the current definition. Overloading is not taken care 
of properly, protection levels are underspecified and underimplemented, 
property syntax is broken, tuples are a mess. Also there's no 64-bit 
implementation. All that stuff is important and relatively urgent.


Andrei