The last years have witnessed a flurry of new results in the area of partial evaluation. These tutorial notes survey the field and present a critical assessment of the state of the art. 1 Introduction Partial evaluation is a source-to-source program transformation technique for specializing programs with respect to parts of their input. In essence, partial evaluation removes layers of interpretation. In the most general sense, an interpreter can be defined as a program whose control flow is determined by its input data. As Abelson points out, [43, Foreword], even programs that are not themselves interpreters have important interpreter-like pieces. These pieces contain both compile-time and run-time constructs. Partial evaluation identifies and eliminates the compile-time constructs. 1.1 A complete example We consider a function producing formatted text. Such functions exist in most programming languages (e.g., format in Lisp and printf in C). Figure 1 displays a formatting functio...

Abstract. Type-directed partial evaluation stems from the residualization of arbitrary static values in dynamic contexts, given their type. Its algorithm coincides with the one for coercing asubtype value into a supertype value, which itself coincides with the one of normalization in the-calculus. Type-directed partial evaluation is thus used to specialize compiled, closed programs, given their type. Since Similix, let-insertion is a cornerstone of partial evaluators for callby-value procedural programs with computational e ects. It prevents the duplication of residual computations, and more generally maintains the order of dynamic side e ects in residual programs. This article describes the extension of type-directed partial evaluation to insert residual let expressions. This extension requires the userto annotate arrowtypes with e ect information. It is achieved by delimiting and abstracting control, comparably to continuation-based specialization in direct style. It enables type-directed partial evaluation of e ectful programs (e.g.,ade nitional lambda-interpreter for an imperative language) that are in direct style. The residual programs are in A-normal form. 1

Lambda-lifting and lambda-dropping respectively transform a blockstructured functional program into recursive equations and vice versa.

Type-directed partial evaluation stems from the residualization of static values in dynamic contexts, given their type and the type of their free variables. Its algorithm coincides with the algorithm for coercing a subtype value into a supertype value, which itself coincides with Berger and Schwichtenberg's normalization algorithm for the simply typed -calculus. Type-directed partial evaluation thus can be used to specialize a compiled, closed program, given its type.

BRICS Report Series RS-98-1 ISSN 0909-0878 January 1998 Copyright c fl 1998, BRICS, Department of Computer Science University of Aarhus. All rights reserved.

The last years have witnessed a flurry of new results in the area of partial evaluation. These tutorial notes survey the field and present a critical assessment of the state of the art. 1 Introduction Partial evaluation is a source-to-source program transformation technique for specializing programs with respect to parts of their input. In essence, partial evaluation removes layers of interpretation. In the most general sense, an interpreter can be defined as a program whose control flow is determined by its input data. As Abelson points out, [43, Foreword], even programs that are not themselves interpreters have important interpreter-like pieces. These pieces contain both compile-time and runtime constructs. Partial evaluation identifies and eliminates the compile-time constructs. 1.1 A complete example We consider a function producing formatted text. Such functions exist in most programming languages (e.g., format in Lisp and printf in C). Figure 1 displays a formatting function ...

s from the Third Workshop Flemming Nielson (editor) October 1993 1 Introduction The third DART workshop took place on Thursday August l9th and Friday August 20th at the Department of Computer Science (DIKU) at the University of Copenhagen; it was organized by Mads Rosendahl and others at DIKU, and Torben Amtoft and Susanne Brønberg helped producing this report. The first day comprised survey presentations whereas the second contained more research oriented talks. The primary aim of the workshop was to increase the awareness of DART participants for each other's work, to stimulate collaboration between the di#erent groups, and to inform Danish industry about the skills possessed by the groups. The DART project started in March 1991 (prematurely terminating a smaller project on Formal Implementation, Transformation and Analysis of Programs) and is funded by the Danish Research Councils as part of the Danish Research Programme on Informatics. To date it has received about 8 million Danis...