clisp-devel

&key and how it's used

[Yves S. G. <you...@gm...>]

Hi all,

   I'm reading this chapter of gigamonkeys.

http://www.gigamonkeys.com/book/practical-a-simple-database.html

2/3 down the page, I see the following methods:

http://bin.cakephp.org/view/1169646936

Now, where I'm drawing a complete and utter blank is 1) how *db* is
accessed, that's where all the data is held and 2) what the heck is &key?

If I'm missing something absurdly obvious, please feel free to point it out.

Re: &key and how it's used

[Pascal J. B. <pj...@in...>]

"Yves S. Garret" <you...@gm...> writes:

> Hi all,
>
>    I'm reading this chapter of gigamonkeys.
>
> http://www.gigamonkeys.com/book/practical-a-simple-database.html
>
> 2/3 down the page, I see the following methods:
>
> http://bin.cakephp.org/view/1169646936
>
> Now, where I'm drawing a complete and utter blank is 1) how *db* is
> accessed, that's where all the data is held and 2) what the heck is
> &key?
>
> If I'm missing something absurdly obvious, please feel free to point it out.
>

This is not the right place to ask that.


https://lists.sourceforge.net/lists/listinfo/clisp-devel

    This mailing list is for the developers of the CLISP implementation
    of ANSI Common Lisp.  It is the proper forum for enhancement
    requests, design discussions, source code patches, pre-release
    announcements, etc. and also for those support questions which are
    not appropriate for the users' list. 


https://lists.sourceforge.net/lists/listinfo/clisp-list

    This mailing list is for users of the CLISP implementation of Common
    Lisp by Bruno Haible and Michael Stoll. It is the proper forum for
    questions about CLISP and also bug reports, compatibility issues,
    problems of CLISP on specific platforms, enhancement of CLISP,
    miscellaneous comments, etc. 

Stretching it, your question could enter the "miscellaneous comments"
category, but since it really has nothing to do with clisp specifically,
but more with Common Lisp in general, you should be asking it on:
news://comp.lang.lisp


&key is described in chapter "5. Functions" of "Practical Common Lisp".
Lambda Lists are explained in section "3.4 Lambda Lists" of CLHS.

-- 
__Pascal Bourguignon__                     http://www.informatimago.com/
A bad day in () is better than a good day in {}.

Re: &key and how it's used

[Yves S. G. <you...@gm...>]

Odd.  I've asked questions here before and got answers.  If I'm wrong, then
I will re-ask the question in the appropriate location.

Thanks for the heads up.

On Sun, Jun 17, 2012 at 3:08 PM, Pascal J. Bourguignon <
pj...@in...> wrote:

> "Yves S. Garret" <you...@gm...> writes:
>
> > Hi all,
> >
> >    I'm reading this chapter of gigamonkeys.
> >
> > http://www.gigamonkeys.com/book/practical-a-simple-database.html
> >
> > 2/3 down the page, I see the following methods:
> >
> > http://bin.cakephp.org/view/1169646936
> >
> > Now, where I'm drawing a complete and utter blank is 1) how *db* is
> > accessed, that's where all the data is held and 2) what the heck is
> > &key?
> >
> > If I'm missing something absurdly obvious, please feel free to point it
> out.
> >
>
> This is not the right place to ask that.
>
>
> https://lists.sourceforge.net/lists/listinfo/clisp-devel
>
>    This mailing list is for the developers of the CLISP implementation
>    of ANSI Common Lisp.  It is the proper forum for enhancement
>    requests, design discussions, source code patches, pre-release
>    announcements, etc. and also for those support questions which are
>    not appropriate for the users' list.
>
>
> https://lists.sourceforge.net/lists/listinfo/clisp-list
>
>    This mailing list is for users of the CLISP implementation of Common
>    Lisp by Bruno Haible and Michael Stoll. It is the proper forum for
>    questions about CLISP and also bug reports, compatibility issues,
>    problems of CLISP on specific platforms, enhancement of CLISP,
>    miscellaneous comments, etc.
>
> Stretching it, your question could enter the "miscellaneous comments"
> category, but since it really has nothing to do with clisp specifically,
> but more with Common Lisp in general, you should be asking it on:
> news://comp.lang.lisp
>
>
> &key is described in chapter "5. Functions" of "Practical Common Lisp".
> Lambda Lists are explained in section "3.4 Lambda Lists" of CLHS.
>
> --
> __Pascal Bourguignon__                     http://www.informatimago.com/
> A bad day in () is better than a good day in {}.
>

Re: &key and how it's used

[Sam S. <sd...@gn...>]

> * Yves S. Garret <lbh...@tz...> [2012-06-17 14:20:13 -0400]:
>>
>  1) how *db* is accessed, that's where all the data is held and

(defun select (selector-fn)
  (remove-if-not selector-fn *db*))
 
(defun where (&key title artist rating (ripped nil ripped-p))
  #'(lambda (cd)
    (and
      (if title    (equal (getf cd :title)  title)  t) 
      (if artist   (equal (getf cd :artist) artist) t)
      (if rating   (equal (getf cd :rating) rating) t)
      (if ripped-p (equal (getf cd :ripped) ripped) t))))

SELECT returns elements of *DB* which satisfy SELECTOR-FN
WHERE returns a function which __APPARENTLY__ can be used as an argument
to SELECT.
e.g.,
(select (where :title "foo"))
will return the objects with the given title.


> 2) what the heck is &key?

a lambda list keyword.
http://www.lispworks.com/documentation/HyperSpec/Body/03_da.htm

it is a way to pass optional arguments to functions in a position
independent way.
e.g.:

(defun foo (&key (a 1) (b 2) (c 3))
  (list a b c))

(foo :b 10) => (1 10 3)
(foo :a 4 :c 5) => (4 2 5)
(foo :c 5 :a 4) => (4 2 5)

> If I'm missing something absurdly obvious, please feel free to point it out.

You might get a more detailed and informative reply to such a general
Lisp question on the comp.lang.lisp newsgroup.

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