A concurrent lambda-calculus with promises and futures

Abstract

Concurrency plays an important role in programming language design. Logic variables in the form of futures and promises provide a means of synchronization and communication in concurrent computation. Futures and promises, which differ from general logic variables in that a distinction is made between reading and writing them, have been introduced previously. However, no formal operational semantics has been provided for promises. In order to formally investigate properties of futures and promises in a functional setting, a concurrent lambda-calculus extended with futures and promises is presented. It is intended to provide a computation model for the programming language Alice. We prove the calculus confluent, and give a proof showing strong normalization in the simply typed case without promises. Further, we introduce a type system so as to statically enforce proper use of promises in the calculus.