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From: Drew Adams <drew.adams@oracle.com>
To: uzibalqa <uzibalqa@proton.me>
Cc: Platon Pronko <platon7pronko@gmail.com>,
	uzibalqa via Users list for the GNU Emacs text editor
	<help-gnu-emacs@gnu.org>
Subject: RE: [External] : Determine whether a list is an alist
Date: Thu, 13 Jul 2023 16:07:49 +0000	[thread overview]
Message-ID: <CO6PR10MB5473021C061A351009904ECBF337A@CO6PR10MB5473.namprd10.prod.outlook.com> (raw)
In-Reply-To: <NmVeAIqQQ2YUPDg6_9AlFZzpEB1TZQzvBwUqZQeDfAbjfOqv0TyebM8pQmSIxnLfRx4QDQ82ETPXHGKMvR6WYy9dq-PaN5YX6zALp1YbrlQ=@proton.me>

> > In many (most?) cases you don't really care
> > whether each element of the list is a cons - you
> > just want to retrieve the first match, and you
> > only want to traverse then entire list if you
> > have to (i.e., when there's no match or the last
> > element matches), and you don't want to traverse
> > it more than once.
> 
> If I want to print the alist in (Key . Value) way, how would one skip
> extraneous (non-cons) list entries ?

`dolist' is your friend.

Printing is a side-effect thingie.  `dolist' is
a natural for iterating over a list, performing
side effects.  Just test each list element and
do what you want with it - that can include
doing nothing with it.  "Extraneous" is in the
eye of the caller-beholder.

This is no different from C, Fortran, assembler,
etc., except that Lisp gives you easy to use
lists and list iterators, ready-made.

LISP: LISt Processing.

  parent reply	other threads:[~2023-07-13 16:07 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-13 10:40 Determine whether a list is an alist uzibalqa
2023-07-13 14:31 ` [External] : " Drew Adams
2023-07-13 14:40   ` Platon Pronko
2023-07-13 15:40     ` Drew Adams
2023-07-13 15:44       ` Drew Adams
2023-07-13 15:49       ` Platon Pronko
2023-07-13 15:56         ` Drew Adams
2023-07-13 15:57       ` uzibalqa
2023-07-13 16:06         ` Platon Pronko
2023-07-13 16:14           ` Drew Adams
2023-07-13 16:07         ` Drew Adams [this message]
2023-07-13 16:12           ` Robert Pluim
2023-07-13 16:16             ` Drew Adams
2023-07-13 15:59       ` Drew Adams
2023-07-13 14:42   ` uzibalqa

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