Sharing a Perspective on the lambda Calculus

International audienceThe lambda calculus models the core of functional programming languages. This essay discusses a gap between the theory of the lambda calculus and functional languages, namely the fact that the former does not give a status to sharing, the essential ingredient for efficiency in the latter.The essay provides an overview of the perspective of the author, who has been and still is studying sharing from various angles. In particular, it explains how sharing impacts the equational and denotational semantics of the lambda calculus, breaking some expected properties, and demanding the development of new, richer semantics of the lambda calculus