Author : Antoine Doucet
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (14 download)
Book Synopsis Adding Hygiene to Gambit Scheme by : Antoine Doucet
Download or read book Adding Hygiene to Gambit Scheme written by Antoine Doucet and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Scheme programming language is known for its powerful macro system. With Scheme source code represented as actual Scheme data, macro transformations allow the programmer, using that data, to act directly on the underlying abstract syntax tree. Macro transformations use a similar syntax to regular procedures but, they define procedures meant to be executed at compile time. Those procedures return an abstract syntax tree representation to be substituted at the transformer's call location. Procedures executed at compile-time use the same language power as run-time procedures. With the macro system, the programmer can create specialized syntax rules without additional performance costs. This also allows for code abstractions without the expected run-time cost of closure creations. Scheme's representation of source code using values inherits that virtue from the Lisp programming language. Source code is represented as a list of symbols, or lists of other lists: a structure coined S-expressions. However, with this simplistic approach, accidental name clashes can occur. The binding to which an identifier refers to is determined by the lexical context of that identifier. By moving an identifier around in the abstract syntax tree, it can be caught within the lexical context of another binding definition with the same name. This can cause unexpected behavior for programmers as the choice of names can create substantial changes in the program. Accidental name clashes can be manually fixed in the code, using name obfuscation, for instance. However, the programmer becomes responsible for the program's safety. The automatic preservation of referential transparency is called hygiene and was thoroughly studied in the context of lambda calculus and Lisp-like languages. The latest Scheme revised report, used as a specification for the language, extend the language with hygienic macro transformations. Up to this point, the Gambit Scheme implementation wasn't providing a built-in hygienic macro system. As a contribution, we re-implemented Gambit's macro system to support hygienic transformations at its core. The algorithm we chose is based on the set of scopes algorithm, implemented in the Racket language by Matthew Flatt. The Racket language is heavily based on Scheme but, diverges on some core features. One key aspect of the Racket language is its extensive hygienic syntactic macro system, on which most core features are built on: the algorithm was robustly tested in that context. In this thesis, we will give an overview of the Scheme language and its syntax. We will state the hygiene problem and describe different strategies used to enforce hygiene automatically. Our algorithmic choice is then justified and formalized. Finally, we present the original Gambit macro system and explain the changes required. We also provide a validity and performance analysis, comparing the original Gambit implementation to our new system.
