PSN implies SN

Emmanuel Polonovski (1)

1 PPS - Preuves, Programmes et Systèmes

In the framework of explicit subsitutions there is two termination properties: preservation of strong normalization (PSN), and strong normalization (SN). Since there are not easily proved, only one of them is usually established (and sometimes none). We propose here a connection between them which helps to get SN when one already has PSN. For this purpose, we formalize a general proof technique of SN which consists in expanding substitutions into ``pure'' lambda-terms and to inherit SN of the whole calculus by SN of the ``pure'' calculus and by PSN. We apply it successfully to a large set of calculi with explicit substitutions, allowing us to establish SN, or, at least, to trace back the failure of SN to that of PSN.

Mots clés: lambda-calculus; explicit substitutions; termination; preservation of termination

Domaines: Logique en informatique [cs.LO]

Emmanuel Polonovski. PSN implies SN. HOR, 2004, Aachen, Germany. pp.78-83. ⟨hal-00384961⟩