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RE: [External] : Determine whether a list is an alist
From: |
Drew Adams |
Subject: |
RE: [External] : Determine whether a list is an alist |
Date: |
Thu, 13 Jul 2023 16:07:49 +0000 |
> > 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.
RE: [External] : Determine whether a list is an alist, uzibalqa, 2023/07/13