Abstract

We describe an extension of Visual Basic 9.0 with asynchronous concurrency constructs – join patterns – based on the join calculus. Our design of Concurrent Basic (CB) builds on earlier work on Polyphonic C# and Comega. Since that work, the need for language-integrated concurrency has only grown, both due to the arrival of commodity, multi-core hardware, and the trend for Rich Internet Applications that rely on asynchronous client-server communication to hide latency. Unlike its predecessors, CB adopts an event-like syntax that should be familiar to existing VB programmers. Coupled with Generics, CB allows one to declare re-useable concurrency abstractions that were clumsy to express previously. CB removes its ancestors’ inconvenient inheritance restriction, while providing new extensibility points useful in practical applications that must co-exist with or want to exploit alternative threading models available on the platform. CB is implemented as an extension of the production VB 9.0 compiler.