We propose a new extension to the purely functional programming language Haskell that supports compile-time meta-programming. The purpose of the system is to support the algorithmic construction of programs at compile-time. The ability to generate code at compile time allows the programmer to implement such features as polytypic programs, macro-like expansion, user directed optimization (such as inlining), and the generation of supporting data structures and functions from existing data structures and functions. Our design is being implemented in the Glasgow Haskell Compiler, ghc. 1

Abstract. Generic programming aims to increase the flexibility of programming languages, by expanding the possibilities for parametrization — ideally, without also expanding the possibilities for uncaught errors. The term means different things to different people: parametric polymorphism, data abstraction, meta-programming, and so on. We use it to mean polytypism, that is, parametrization by the shape of data structures rather than their contents. To avoid confusion with other uses, we have coined the qualified term datatype-generic programming for this purpose. In these lecture notes, we expand on the definition of datatype-generic programming, and present some examples of datatypegeneric programs. We also explore the connection with design patterns in object-oriented programming; in particular, we argue that certain design patterns are just higher-order datatype-generic programs. 1

We present the TIC (Transactions with Isolation and Cooperation) model for concurrent programming. TIC adds to standard transactional memory the ability for a transaction to observe the effects of other threads at selected points. This allows transactions to cooperate, as well as to invoke nonrepeatable or irreversible operations, such as I/O. Cooperating transactions run the danger of exposing intermediate state and of having other threads change the transaction’s state. The TIC model protects against unanticipated interference by having the type system keep track of all operations that may (transitively) violate the atomicity of a transaction and require the programmer to establish consistency at appropriate points. The result is a programming model that is both general and simple. We have used the TIC model to re-engineer existing lock-based applications including a substantial multi-threaded web mail server and a memory allocator with coarse-grained locking. Our experience confirms the features of the TIC model: It is convenient for the programmer, while maintaining the benefits of transactional memory.

We present the design of the Boost interval arithmetic library, a C++ library designed to efficiently handle mathematical intervals in a generic way. Interval computations are an essential tool for reliable computing. Increasingly a number of mathematical proofs have relied on global optimization problems solved using branch-andbound algorithms with interval computations; it is therefore extremely important to have a mathematically correct implementation of interval arithmetic. Various implementations exist with diverse semantics. Our design is unique in that it uses policies to specify three independent variable behaviors: rounding, checking, comparisons. As a result, with the proper policies, our interval library is able to emulate almost any of the specialized libraries available for interval arithmetic, without any loss of performance nor sacrificing the ease of use. This library is openly available at www.boost.org.

We report on the design objectives and initial design of a new discrete-event network simulator for the research community. Creating Yet Another Network Simulator (yans,

cJ is an extension of Java that allows supertypes, fields, and methods of a class or interface to be provided only under some static subtyping condition. For instance, a cJ generic class, C<P>, may provide a member method m only when the type provided for parameter P is a subtype of a specific typeQ. From a practical standpoint, cJ adds to generic Java classes and interfaces the ability to express case-specific code. Unlike conditional compilation techniques (e.g., the C/C++ “#ifdef ” construct) cJ is statically type safe and maintains the modular typechecking properties of Java generic classes: a cJ generic class can be checked independently of the code that uses it. Just like regular Java, checking a cJ class implies that all uses are safe, under the contract for type parameters specified in the class’s signature. As a specific application, cJ addresses the well-known shortcomings of the Java Collections Framework (JCF). JCF data structures often throw run-time errors when an “optional ” method is called upon an object that does not support it. Within the constraints of standard Java, the authors of the JCF had to either sacrifice static type safety or suffer a combinatorial explosion of the number of types involved. cJ avoids both problems, maintaining both static safety and conciseness.

The Lambda Library (LL) adds a form of lambda functions to C++, which are common in functional programming languages. The LL is implemented as a template library using standard C++; thus no language extensions or preprocessing is required. The LL consists of a rich set of tools for defining unnamed functions. Particularly, these unnamed functions work seamlessly with the generic algorithms in the C++ Standard Library. The LL offers significant improvements, in terms of generality and ease of use, compared to the current tools in the C++ Standard Library.

CLAM is a C++ framework that offers a complete development and research platform for the audio and music domain. Apart from offering an abstract model for audio systems, it also includes a repository of processing algorithms and data types as well as a number of tools such as audio or MIDI input/output. All these features can be exploited to build crossplatform applications or to build rapid prototypes to test signal processing algorithms. In this article we will review the main features included in the framework. We will also present some of the applications that have been developed and can be used by themselves. We will finally introduce the newest tools that have been added in order to use the framework as a rapid prototyping tool. 1.

Design patterns are reusable abstractions in object-oriented software. However, using current programming languages, these elements can only be expressed extra-linguistically: as prose, pictures, and prototypes. We believe that this is not inherent in the patterns themselves, but evidence of a lack of expressivity in the languages of today. We expect that, in the languages of the future, design patterns will be expressible as reusable library code. Indeed, we claim that the languages of tomorrow will suffice; the future is not far away. The necessary features are higher-order and datatypegeneric constructs; these features are already or nearly available now. We argue the case by presenting higher-order datatypegeneric programs capturing ORIGAMI, a small pattern language of recursive data structures.

this paper, "polymorphism" means parametric polymorphism by default