Macros That Work

9 pagesThis paper describes a modified form of Kohlbecker's algorithm for reliably hygienic (capture-free) macro expansion in block-structured languages, where macros are source-tos-ource transformations specified using a high-level pattern language. Unlike previous algorithms, the modified algorithm runs in linear instead of quadratic time, copies few constants, does not assume that syntactic keywords ( e.g. if) are reserved words, and allows local (scoped) macros to refer to lexical variables in a referentially transparent manner. Syntactic closures have been advanced as an alternative to hygienic macro expansion. The problem with syntactic closures is that they are inherently low-level and therefore difficult to use correctly, especially when syntactic keywords are not reserved. It is impossible to construct a pattern-based, automatically hygienic macro system on top of syntactic closures because the pattern interpreter must be able to determine the syntactic role of an identifier (in order to close it in the correct syntactic environment) before macro expansion has made that role apparent. may be viewed as a book-keeping technique for deferring such decisions until macro expansion is locally complete. Building on that insight, this paper unifies and extends the competing paradigms of hygienic macro expansion and syntactic closures to obtain an algorithm that combines the benefits of both . Several prototypes of a complete macro system for Scheme have been based on the algorithm presented here

Recent Developments and Future Directions in Lisp-Stat

1 online resource (PDF, 16 pages

DRAFT : Task System and Item Architecture (TSIA)

During its execution, a task is independent of all other tasks. For an application which executes in terms of tasks, the application definition can be free of the details of the execution. Many projects have demonstrated that a task system (TS) can provide such an application with a parallel, distributed, heterogeneous, adaptive, dynamic, real-time, interactive, reliable, secure or other execution. A task consists of items and thus the application is defined in terms of items. An item architecture (IA) can support arrays, routines and other structures of items, thus allowing for a structured application definition. Taking properties from many projects, the support can extend through to currying, application defined types, conditional items, streams and other definition elements. A task system and item architecture (TSIA) thus promises unprecedented levels of support for application execution and definition.Comment: vii+244 pages, including 126 figures of diagrams and code examples. Submitted to Springer Verlag. For further information see http://www.tsia.or

A Module System for Scheme

This paper presents a module system designed for largescale programming in Scheme. The module system separates specifications of objects from their implementations, permitting the separate development, compilation, and testing of modules. The module system also includes a robust macro facility