Discrimination by Parallel Observers: The Algorithm

AbstractThe main result of the paper is a constructive proof of the following equivalence: two pureλ-terms are observationally equivalent in the lazy concurrentλ-calculusiffthey have the same Lévy–Longo trees. An algorithm which allows to build a context discriminating any two pureλ-terms with different Lévy–Longo trees is described. It follows that contextual equivalence coincides with behavioural equivalence (bisimulation) as considered by Sangiorgi. Another consequence is that the discriminating power of concurrent lambda contexts is the same as that of Boudol–Laneve's contexts with multiplicities