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Describe assoc-default.

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Richard M. Stallman 1998-08-08 23:16:07 +00:00
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lispref/lists.texi
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@ -1438,6 +1438,26 @@ becomes clearer if the association is written in dotted pair notation:
@end smallexample
@end defun
@tindex assoc-default
@defun assoc-default key alist test default
This function searches @var{alist} for a match for @var{key}. For each
element of @var{alist}, it compares the element (if it is an atom) or
the element's @sc{car} (if it is a cons) against @var{key}, by calling
@var{test} with two arguments: the element or its @sc{car}, and
@var{key}. The arguments are passed in that order so that you can get
useful results using @code{string-match} with an alist that contains
regular expressions (@pxref{Regexp Search}). If @var{test} is omitted
or @code{nil}, @code{equal} is used for comparison.
If an alist element matches @var{key} by this criterion,
then @code{assoc-default} returns a value based on this element.
If the element is a cons, then the value is the element's @sc{cdr}.
Otherwise, the return value is @var{default}.
If no alist element matches @var{key}, @code{assoc-default} returns
@code{nil}.
@end defun
@defun copy-alist alist
@cindex copying alists
This function returns a two-level deep copy of @var{alist}: it creates a