Implementing a Lazy Functional Logic Language with Disequality Constraints
Herbert Kuchen, Francisco J. López-Fraguas, Juan José Moreno-Navarro, Mario Rodríguez-Artalejo · 1992
In this paper, we investigate the implementation of a lazy functional logic language (in particular the language BABEL [MR88, MR92]) which uses disequality constraints for solving equations and building answers. We specify a new operational semantics which combines lazy narrowing with disequality constraints and we define an abstract machine tailored to the execution of BABEL programs according to this semantics. The machine is designed as a quite natural extension of a lazy graph narrowing machine [MKLR90]. Disjunctions of disequalities are handled using the backtracking mechanism.