Two algorithms are considered for implementation in Prolog. It is shown that these algorithms cannot be implemented in pure Prolog and retain their nominal time complexity. It is shown that a generalization of Lisp's rplaca/rplacd construct suffices for these algorithms. We give a method for the implementation of the new construct, rplacarg, on a structure-copying Warren Abstract Machine and discuss implementation for a structure-sharing Warren Abstract Machine. We show how rplacarg may be implemented in CProlog using only pure Prolog constructs and the var construct. We show that var can be implemented in terms of the Prolog not primitive. We show that rplacarg can be used to implement multidimensional arrays efficiently in Prolog.
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Data Structures and Destructive Assignment in Prolog
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