Abstract

Mezzo is a programming language in the tradition of ML, where the usual concept of a type is replaced by a more precise notion of a /permission/. Permissions allow one to describe in an accurate manner how objects are laid out in memory—more specifically, permissions describe the shape of the heap. Permissions also enable the programmer to control ownership of objects, which turns out to be paramount in a concurrent setting.

Permissions allow one to state more powerful invariants about a program, while still remaining within the bounds of a type system; therefore, programs that previously could not be type-checked in ML can be written in Mezzo. I will demonstrate the usage of patterns such as progressive initialization and strong update. I will also showcase a work-in-progress prototype type-checker, and give hints about future challenges, such as inference, good primitives for concurrency, and a proof of soundness.