Re: syntax: anonymous vs. named functions

[Andreas Politz <politza@fh-trier.de>]

Drew Adams wrote:
[...]
> 
> The reason that a lambda form is not allowed as a functional COLLECTION argument
> is that although a lambda form can generally be used as a function, it
> _evaluates_ to a list (whose car is `lambda' etc. - that is, to itself).
> 
> And since COLLECTION can also be an explicit list of candidates, it would be
> problematic to distinguish the intention of passing an argument whose value is a
> list that has the form (lambda (...) ...). This is a feature of Lisp's
> program=data quality.

Mhh, more likely a problem of elisp.

CL-USER> (functionp #'(lambda nil))
T
CL-USER> (functionp '(lambda nil))
NIL

In elisp both expressions evaluate as T. I like the CL feature better ;)

-ap
> 
>> ps, does the collection function really need to accept all three
>> arguments (string, predicate and t/nil/lambda)?
> 
> Yes. It need not _use_ all three, or even any of them, to do its job, but it
> must accept three arguments. The primitive Emacs completion functions depend on
> it having such a signature.
> 
>> i know you say that
>> (do-completion (string)) is a function application, but what would a
>> function look like in this case?  just like this: do-completion (that
>> is, a simple evaluated symbol)?  
> 
> Correct. You would pass the function `do-completion' this way:
> 
>  (completing-read "Name: " #'do-completion nil t)
> 
> 
>