CONCEPT
        alists

LAST UPDATE
        2 Mar 92 21:10:21 GMT

AUTHOR
        From: amylaar@mcshh.hanse.de (Joern Rennecke)
        Subject: general documentation on alists

DESCRIPTION
        Alists provide a fast and convenient way to access data
        associatively.

        Alists are implemented as arrays of arrays, the first being
        the array holding the keys, the others arrays holding
        associated data. An empty alist is an array of empty arrays.

        Note that the the dimensions of the arrays are used the other
        way than in lisp to allow for faster searching.

        Keys have to be of type integer, string or object. Types can
        be mixed.

        The search functions return an undefined value when another
        list is given in place of a presorted key list.

        A list with non-numeric keys retrieved by restore_object() has
        to be readjusted by using order_alist(), especially after
        reboot.

        Deleting an entry can safely be done with exclude_array as
        long as all associated data lists are treated like the key
        array; index finding for such purposes can be done with assoc.

        Typical applications: holding administrary information about
        wizards, list of visitors in a pub, list of customers having
        some sort of credit, information remembered about items etc.

NOTE
        The main use of alists, storing data associatively, is now
        better performed by mappings. Alists are needed for more
        extreme situations only.

CAVEATS
         A maximum array size of 1000 might prove to be to small.

SEE ALSO
        mappings(LPC), order_alist(E), insert_alist(E), assoc(E),
        transpose_array(E)
