Paths in the lambda-calculus. Three years of communications without understanding

摘要

Since the rebirth of /spl lambda/-calculus in the late 1960s, three major theoretical investigations of /spl beta/-reduction have been undertaken: (1) Levy's (1978) analysis of families of redexes (and the associated concept of labeled reductions); (2) Lamping's (1990) graph-reduction algorithm; and (3) Girard's (1988) geometry of interaction. All three studies happened to make crucial (if not always explicit) use of the notion of a path, namely and respectively: legal paths, consistent paths and regular paths. We prove that these are equivalent to each other.