The impact of Domain Specific Languages (DSLs) on software design is considerable. They allow programs to be more concise than equivalent programs written in a high-level programming languages. They relieve programmers from making decisions about data-structure and algorithm design, and thus allows solutions to be constructed quickly. Because DSL's are at a higher level of abstraction they are easier to maintain and reason about than equivalent programs written in a highlevel language, and perhaps most importantly they can be written by domain experts rather than programmers. The problem is that DSL implementation is costly and prone to errors, and that high level approaches to DSL implementation often produce inefficient systems. By using two new programming language mechanisms, program staging and monadic abstraction, we can lower the cost of DSL implementations by allowing reuse at many levels. These mechanisms provide the expressive power that allows the construction of many compil...

Abstract. The iData Toolkit is a toolkit that allows programmers to create interactive, type-safe, dynamic web applications with state on a high level of abstraction. The key element of this toolkit is the iData element. An iData element is a form that is generated automatically from a type definition and that can be plugged in in the web page of a web application. In this paper we show how this automatic generation of forms has been implemented. The technique relies essentially on generic programming. It has resulted in a concise and flexible implementation. The kernel of the implementation can be reused for any graphical package. The iData Toolkit is an excellent demonstration of the expressive power of modern generic (poly-typical) programming techniques. 1

Abstract. In these lecture notes we present a novel toolkit to program web applications with that have dynamic, complex behavior based on interconnect forms. This toolkit is the iData Toolkit. We demonstrate that it allows programmers to create web applications on a level of abstraction that is comparable with ‘ordinary ’ functional style programs. Programmers have the freedom to develop their own data structures and program with them. The iData Toolkit is able to generate a web application from these data types, making use of advanced programming concepts such as generic programming. The programmer need not be aware of this. We have tried to keep the iData Toolkit api as simple as possible. 1

Programming GUIs with conventional GUI APIs is notoriously tedious. In these notes we present the GEC toolkit in which the programmer can create user interfaces without any knowledge of lowlevel I/O handling. Instead, he works with Graphical Editor Components (GEC). A GEC is an interactive component that is automatically derived from an arbitrary monomorphic data type, including higher order types.

With generic functional programming techniques, we have eased GUI programming by constructing a programming toolkit with which one can create GUIs in an abstract and compositional way, using type-directed Graphical Editor Components (GECs). In this toolkit, the programmer specifies a GUI by means of a data model instead of lowlevel GUI programming. In earlier versions of this toolkit, the data model must have a first-order type. In this paper we show that the programming toolkit can be extended in two ways, such that the data model can contain higher-order types. We added support for dynamic polymorphic higher-order editors using the functional shell Esther. By combining the earlier developed techniques of generic GECs, abstract editors, we also added statically typed higher-order editors. In principle this solution extends our GUI programming toolkit with the full expressive power of functional programming languages.

In writing this paper we had two goals. First, to promote MetaML, a programming language for writing staged programs, and second, to demonstrate that staging a program can have significant benefits. We do this by example: the derivation of an executable compiler for a small language. We derive the compiler in a rigorous fashion from a semantic description of the language. This is done by staging a denotational semantics, expressed as a monadic interpreter. The compiler is a program generator, taking a program in the source language "a while-program" as input and producing an ML program as target. The ML program produced is in a restricted subset of ML over which the programmer has complete control. It is encapsulated in a special data-structure called code. The meta-programming capabilities of MetaML allow this data-structure to be directly executed "run-time code generation", or to be analysed. We illustrate this analysis of generated code to build a source to source transf...

Abstract. The GEC Toolkit offers to programmers a high-level, generic style of programming Graphical User Interfaces (GUIs). Programmers are not concerned with low-level widget plumbing. Instead, they use mathematical data models that reflect both the application logic and the visualisation. The data models and the logic are expressed as standard functional style data types and functions over these data types. This significantly brings down the learning effort. In this paper we present an improved programming method of this toolkit and illustrate it by means of a complicated case study: that of a family tree editor. The new programming method brings GUI programming into the reach of every novice functional programmer. 1

Abstract.. This paper presents a library for the run-time construction and specialisation of generic or polytypic functions. This library utilises the type information that is available in dynamics to implement generic functions on their values. The library closely follows the static generic framework, both in its use and in its implementation. It can dynamically construct generic operations ranging from equality, map and parsers to pretty printers and generic graphical editors. A special feature of the library is that it can also be used to derive meaningful specialisations of generic functions that operate on the type representation of the dynamic. 1