From 42101e875de1fa1388dd76a6f4f18054c16d24ef Mon Sep 17 00:00:00 2001 From: Luc Teirlinck Date: Tue, 20 Jan 2004 23:06:28 +0000 Subject: [PATCH] (Sets And Lists): Add delete-dups. --- lispref/lists.texi | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/lispref/lists.texi b/lispref/lists.texi index b123de5ab10..cb033118984 100644 --- a/lispref/lists.texi +++ b/lispref/lists.texi @@ -1223,7 +1223,8 @@ useful example of @code{sort}. A list can represent an unordered mathematical set---simply consider a value an element of a set if it appears in the list, and ignore the order of the list. To form the union of two sets, use @code{append} (as -long as you don't mind having duplicate elements). Other useful +long as you don't mind having duplicate elements). You can remove +@code{equal} duplicates using @code{delete-dups}. Other useful functions for sets include @code{memq} and @code{delq}, and their @code{equal} versions, @code{member} and @code{delete}. @@ -1431,6 +1432,20 @@ be a string and that it ignores differences in letter-case and text representation: upper-case and lower-case letters are treated as equal, and unibyte strings are converted to multibyte prior to comparison. +@end defun + +@defun delete-dups list +This function destructively removes all @code{equal} duplicates from +@var{list} and returns the result. Of several @code{equal} +occurrences of an element in @var{list}, @code{delete-dups} keeps the +last one. + +The value of @var{list} after a call to this function is undefined. +Usually, we store the return value back in @var{list}: + +@example +(setq list (delete-dups list)) +@end example @end defun See also the function @code{add-to-list}, in @ref{Setting Variables}, -- 2.39.2