Re: syntax: anonymous vs. named functions

[Andreas Politz]

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)