Re: apply on dotted argument lists

Hi Bruno,

> * Bruno Haible <[email protected]> [2012-04-13 02:42:16 +0200]:
>
> Moving the discussion from the bug tracker
> https://sourceforge.net/tracker/?func=detail&atid=101355&aid=3517196&group_id=1355
> to the list.

bad idea.
before: both clisp-devel and sf bug tracker knew the reasoning.
now: only clisp-devel does.

>> 1. I don't think you can separate compiled from interpreted here:
>> both are done by apply_closure
>
> The compiled closure is handled in the first part of apply_closure,
> the interpreted one in the last 20 lines of apply_closure. This
> one-liner should produce an error in the interpreted case:

sure.

>> 2. I don't think adding an explicit list check to the evaluator makes
>> much sense.
>
> Why? I think it does: Any useful error message that occurs while a
> user is testing his program in interpreted mode is useful.

what I meant was something like

  object dotted;
  list_length(args,&dotted);
  if (!nullp(dotted))
    goto error_dotted;

>> 3. Bruno, why do you have error_apply_dotted signal a program-error and
>> error_apply_toofew signal an argument-list-dotted error? these look weird:
>> 
>> > (apply #'cons 1)
>> *** - APPLY: dotted argument list given to CONS : 1
>> > (apply #'read-from-string "a" 2)
>> *** - APPLY: argument list given to READ-FROM-STRING is dotted (terminated
>> by 2)
>> 
>> I think the messages (and errors) should be identical.
>
> I agree that the messages are unnecessarily different.
>
> About the error types: Since PROGRAM-ERROR is defined as errors relating
> to "program syntax"
> <http://www.ai.mit.edu/projects/iiip/doc/CommonLISP/HyperSpec/Body/contyp_program-error.html>
> but here we don't have a wrong program (that could be caught at
> compile-time), just wrong data (at runtime), I think that PROGRAM-ERROR
> is wrong here, in both cases.

I am not so sure.  (apply #'foo 1) can be caught at compile time and is
probably second only to (format "..." ...) in frequency.

> But in the first case, CLHS section 3.5.1.2
> <http://www.ai.mit.edu/projects/iiip/doc/CommonLISP/HyperSpec/Body/sec_3-5-1-2.html>
> forces us to signal a PROGRAM-ERROR (or subtype thereof), even though
> it's nonsense.
>
> In the second case, CLHS does not specify which error is signaled
> (see <http://www.ai.mit.edu/projects/iiip/doc/CommonLISP/HyperSpec/Body/fun_apply.html#apply>:
> "Exceptional Situations: None."). Why should we repeat the same nonsense here?

I think Occam requires the same behavior in both cases.
Moreover, your argument-list-dotted is already a subtype of
program-error, so I really see no reason for this dichotomy.

-- 
Sam Steingold (http://sds.podval.org/) on Ubuntu 11.10 (oneiric) X 11.0.11004000
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