RETELL
======

Syntax: (retell <simple-predication> old-value)
           ::= (retell [<relation-name> <instance>
               <new-value>] old-value)

With RETELL it is possible to change the values of
instances. The old instance value can be replaced
by a new value. If the old value is unknown, it can
be replaced by the anonymus variable _.
RETELL returns T, if the knowledge base has been
changed, otherwise NIL.

Example: >(retell [options Siemens-Nixdorf
             1,6GB-harddisk] 1GB-harddisk)
         T

In this case the 1GB-harddisk of the Siemens-
Nixdorf-computer will be replaced by a
1,6GB-harddisk!