Solution

%% The base case: both lists are empty.
%% The result is 0.
dot([],[],0).

%% The recursive case: neither of the lists is empty.
%% For the result, we first compute the dot product of the tails of
%% the two input lists. Then, we add the product of the two heads.
dot([InHead1|InTail1],[InHead2|InTail2],Result) :-
              dot(InTail1,InTail2,ResultTails),
	      Result is (InHead1 * InHead2) + ResultTails.
    

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