[cdr-discuss] Three RFCs

[Ingvar]

Gary King wrote
> Pascal Constanza wrote:
> >> 1. Support a :TEST arg for (E)CASE.
> >
> > I'm not sure what this buys you over a regular cond. Case primarily  
> > exists for efficiency, no?
> 
> Hi Pascal, I see your point _but_ there is also something to be said  
> for efficiency of human code reading and code writing, no? I'd say  
> that case variants let the reader know that all of the tests are of  
> the form "this" is the same as "that" for some notion of "same as" and  
> various "that"s.
> 
> (case <this>
>    (that-1 ...)
>    (that-2 ...)
>    ...)
> 
> whereas cond is saying, do an arbitrary test for each possible branch...
> 
> This may not be enough to argue for adding to  / extending case...

I have mixed feelings about this. On one hand, it is a handy idiom. On the 
other hand, CASE (and ECASE and maybe, to some extent TYPECASE) are by now 
well-ingrained as efficient idioms.

I would personally be happier if there was an  "almost CASE" with user-
controllable test, whose name didn't actually contain "CASE" at all. 
Unfortunately, I don't think SWITCH is a good name, either. I notice that I 
can't see a SELECT in the HyperSpec, maybe that would be a neutral-enough name 
for this sort of construct?

Something along the lines of:
(select (form &optional (test #'eql))
  ...)

With the forms following being similar to the ones used in CASE/ECASE?

It is a handy idiom, in that respect and I have whipped up some in the past 
(though, I must admit, special-purpose ones, each time, rather than a general 
one).

//Ingvar