Commit 42101e87 authored by Luc Teirlinck's avatar Luc Teirlinck

(Sets And Lists): Add delete-dups.

parent 9fa0334c
......@@ -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},
......
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