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Re: list sorting problem

From: Vivek Dasmohapatra
Subject: Re: list sorting problem
Date: 12 Apr 2002 00:09:04 +0100
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.1

"Mary Dalrymple" <address@hidden> writes:

> Can someone help me with the sorting function?  I'm getting the following
> behavior.
[examples deleted]
> One of the list elements disappears.  This happens in Emacs 20.7.1.  Can
> someone tell me what is going on?  Thanks --

M-x describe-function RET sort RET

is your friend:

sort is a built-in function.

Sort LIST, stably, comparing elements using PREDICATE.
Returns the sorted list.  LIST is modified by side effects.
PREDICATE is called with two elements of LIST, and should return T
if the first element is "less" than the second.

In other words, sort destructively alters LIST, and returns a sorted list.
LIST is not guaranteed to be useful after you call sort on it. To sort LIST
in place from your programs pov: 

(setq before (sort before (lambda (a b) (string< (car a) (car b)))))

Just one nuclear family can ruin your whole life.

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