Machine" [BB90], except that there are no "cooling" and "heating" transitions (the process sets of this semantics can be thought of as perpetually "hot" solutions). The concurrent evaluation relation extends "7\Gamma!" to finite sets of terms (i.e., processes) and adds additional rules for process creation, channel creation, and communication. We assume a set of process identifiers, and define the set of processes and process sets as: ß 2 ProcId process IDs p = hß; ei 2 Proc = (ProcId \Theta Exp) processes P 2 Fin(Proc) process sets We often write a process as hß; E[e]i, where the evaluation context serves the role of the program counter, marking the current state of evaluation. Definition4. A process set P is well-formed if for all hß; ei 2 P the following hold: -- FV(e) = ; (e is closed), and -- there is no e 0 6= e, such that hß; e 0 i 2 P. It is occasionally useful to view well-formed process sets as finite maps from ProcId to Exp. If P is a finite set of process state...

This paper describes eXene, a user interface toolkit implemented in a concurrent extension of Standard ML. The design and use of eXene is inextricably woven with the presence of multiple threads and a high-level language. These features replace the object-oriented design of most toolkits, and provide a better basis for dealing with the complexities of user interfaces, especially concerning such aspects as type safety, extensibility, component reuse and the balance between the user interface and other parts of the program. 1

. The idea of making synchronous operations into first-class values is an important one for supporting abstraction and modularity in concurrent programs. This design principle has been used with great success in the concurrent language CML, but what are the limitations of this approach? This paper explains the rationale for first-class synchronous operations, and discusses their use in CML. It also presents some recent and fundamental results about the expressiveness of rendezvous primitives, which define the limitations of synchronous abstractions. 1 Introduction Abstraction is a key tool for managing complexity. The design of programming languages is one area where application of this idea has paid significant dividends. Languages have evolved from providing a fixed set of abstractions of the underlying hardware, such as arithmetic expressions and arrays, to providing support for programmer-defined abstractions, such as abstract data-types and higher-order procedures. By providing ...

The Iris library provides a basis for constructing user interfaces on bitmap displays. Written in C++, it provides a window class as the main data type, along with support for such graphical classes as point, rectangle, font, icon, etc. Windows can be created within windows; this property, along with the derived class notion in C++, allows the user to design complex interface objects built from simpler components in a modular fashion. In addition, a window can specify which input events, ranging from a change in a specific mouse button to a move request, it will accept. This paper provides an introduction to Iris and a discussion of its use.

. Attribute grammars are a valuable tool for constructing compilers and building user interfaces. This paper reports on a system we are developing, called AML (for Attribution in ML), which is an attribute grammar toolkit for building such applications as language-based programming environments using SML. This system builds on the proven technology of efficient attribute evaluation, while using a higher-level foundation for the implementation of interactive systems. It supports a general and uniform platform for building applications that can manipulate attributed terms and allow access to attribute values. We describe the design of the AML system, its current implementation status, and our plans for the future. CR Classification: D.1.1, D.2.6, D.3.4 Key words: attribute grammars, attribute evaluation, functional programming, program generator, programming environments 1. Introduction Attribute grammars provide a formalism for assigning meaning to parse trees of a context-free languag...