Jaffar, J. Efficient unification over infinite terms . In practice, a more expensive algorithm, but simple and well embedded in the whole implemented system, is preferable especially when the applicative context is such that the worst case very seldom, or never, occurs. In our approach this relation is explicitly maintained in the combinatorial structure used for terms. Efficient unification over infinite terms . New Generation Computing, 1984.
Rational trees account for term equations which express cycles.
All of the compiled systems except MProlog and Aquarius are based on the WAM instruction set, but modified and extended to increase performance. Efficient Unification over Infinite Terms . This dichotomy between types of formalism thus seems to dictate the approach to unification that must be taken in a practical parsing system. Unification in an algebra with choice and action prefix. In the presence of infinite processes special provisions are needed to ensure that the program terminates.