Re: What does the argument list in C-h f delete-duplicates mean?

Alan Mackenzie <[email protected]>
Newsgroups gmane.emacs.xemacs.beta
Message-ID <[email protected]>
Hello, Aidan.

On Fri, Jun 05, 2015 at 03:27:45PM +0100, Aidan Kehoe wrote:

> Hello Alan,

>  Ar an cúigiú lá de mí Meitheamh, scríobh Alan Mackenzie: 

>  > When I do C-h f delete-duplicates, the resulting text starts off:

>  > `delete-duplicates' is a built-in function
>  >   -- loaded from "/home/acm/emacs/xemacs.hg/xemacs/src/sequence.c"
>  > (delete-duplicates SEQUENCE &key (TEST #'eql) (KEY #'identity) (START 0) END FROM-END TEST-NOT)

>  > .  What does this mean?  In particular, I have never seen parenthesised
>  > expressions, such as "(TEST #'eql)" inside an argument list before.  The
>  > XEmacs manual (page "Name Help") doesn't explain this.  Are TEST, KEY
>  > and START some sort of optional parameters, or what?

> Yes, they’re optional keyword parameters, as also used, for example, by
> #'make-hash-table. The docstring for defun* goes into more detail on the
> syntax.

Thanks, that's helpful.

> I have been considering moving the extra functionality offered by defun* into
> defun, but there are possible bootstrapping complications; if I do it I’ll
> move the relevant documentation into the defun docstring, if I don’t I’ll add
> a cross-reference to all the C functions that use keywords. Thanks for
> pointing out the weakness in our docs!

> Best,

> Aidan

-- 
Alan Mackenzie (Nuremberg, Germany).

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