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/*  The idea is that 
pdate all the tuples in a relation you call
	update(r(A,...,Z), new_r(A,...,
    where A...Z must be variables, and new_r is a goal or body which
   
putes all the new tuples (unit clauses) including any tuples
    tha
ven't changed.

    Another thing one sometimes wants to do in d
base work is to
    change a set of tuples.  The command











































































































































































































































































































































































































































































































































































































































































