Core-tyco User's Manual Version 0.1 (alpha)

1 What is TyCO? Typed Concurrent Objects-TyCO 5], is essentially the (asynchronous)-calculus plus branching structures. Branching structures appear as a pair of operators: selection (or labeled messages), which replace the output processes of the-calculus, and branching (or objects) which replace the input processes (or preex) of the-calculus. Potentially unbounded behavior is modeled through explicit instantiation of recursive templates. TyCO has the same computational power as the asynchronous-calculus 5] and is reminiscent of the Abadi and Cardelli's &-calculus 1] in the sense that objects are sums of labeled methods (the name self being interpreted as the channel where the object is held) and messages can be seen as asynchronous method invocations. The &-calculus however presents a method update operation which is not present in TyCO. We developed the theoretical framework for an abstract machine capable of executing programs written in a TyCO idiom 3]. The machine is sound and has important runtime properties such as the impossibility of deadlock in well-typed programs 2]. Based in this formal speciication we developed a self-contained abstract machine architecture 4]. In its present form the machine has a single-threaded architecture, with a very small instruction set and a simple memory layout. Our goal is to provide an universal framework for compiling concurrent, process and communication-based programming languages, and providing them with a runtime system. Several such languages can be easily encoded in TyCO, which may be used as an intermediate language. Recursion can be supported through replication or explicit instantiation of template objects. TyCO originally supports recursion through explicit instantiation of template objects. Each recur-sive call within the body of the method must create a new replica of the original object, ensuring that no unnecessary copies are ever created. Replication has the disadvantage that, once created, replicated objects will exist for the duration of the program even if they are only required for a small part of the computation. However, to eeciently support languages where these objects appear we decided to include them in the language deenition. Method invocation is a one-way protocol in TyCO requiring a single step reduction (communication). The abstract machine executes threads-sequences of processes-that are the bodies of methods. All newly created threads are placed at the end of the run-queue. Processes within threads are executed without interference from the scheduler, hence threads cannot be blocked. Threads are identiied with object's methods. This fact allows the deenition of a very clean …