From: Tassilo Horn <tassilo@member.fsf.org>
To: help-gnu-emacs@gnu.org
Subject: Re: Accessing an element in an associativity list
Date: Tue, 09 Sep 2008 16:47:10 +0200 [thread overview]
Message-ID: <87prndfkb5.fsf@thinkpad.tsdh.de> (raw)
In-Reply-To: slrngccud5.32d.joostkremers@j.kremers4.news.arnhem.chello.nl
Joost Kremers <joostkremers@yahoo.com> writes:
Hi!
> (defvar c++-stl-containers
> '(("string" "<string>" "String of char.")
> ("wstring" "<wstring>" "String of wide char (wchar_t).")
> ("vector" "<vector>" "Vectors contain contiguous elements stored as an array.")))
>
>> and I want to do something like this:
>> (index-first 'c++-stl-containers "string" 2)
>> should evaluate to
>> "<string>"
>>
>> Is there any emacs lisp convenience function for accessing a row
>> given its, say, first (key) element?
>
> you can use ASSOC:
>
> (assoc "string" c++-stl-containers)
>
> ===> ("string" "<string>" "String of char.")
For the sake of completeness: To get to "<string>" from the key
"string" you'd use
(cadr (assoc "string" c++-stl-containers))
here, which is a shortcut for
(car (cdr (assoc "string" c++-stl-containers))).
Or you could use one of
(nth 1 (assoc "string" c++-stl-containers))
(second (assoc "string" c++-stl-containers)).
Bye,
Tassilo
prev parent reply other threads:[~2008-09-09 14:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-09 13:07 Accessing an element in an associativity list Nordlöw
2008-09-09 13:28 ` Joost Kremers
2008-09-09 14:47 ` Tassilo Horn [this message]
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