Stratégies Efficaces et Modèles d'Implantation pour les Langages Fonctionnels. (Efficient Strategies and Implementation Models for Functional Languages)

In functional languages, e ciency heavily relies on the choice of an evaluation strategy and an implementation model. We rst develop a λ-calculus with explicit substitutions which avoids the usual problems of substitution and α-conversion, where we can de ne the usual strategies, as well as some strategies with more sharing of computations. We then develop an e cient implementation model for this calculus. To this end, we propose an innovative representation of free variables, rst in the very general setting of higher-order rewriting, then with more details in our particular case. We thus obtain a λ-calculus with explicit substitutions without names nor indices, in which terms are annotated with information about how substitutions should be propagated, which is a suitable implementation model for our strategies. Abstract machines are then de ned, implemented, and experimentally compared to the best known evaluators. Finally, we study the relationship between traditional abstract machines and interaction nets, two common but very di erent implementation models. More precisely, we show how some strategies can be implemented in interaction nets in a very natural way, thus bridging the gap between two models used to implement e cient strategies.