From Lisp S-Expressions to Java Source Code

António Menezes Leitão

The syntax of Lisp languages is based on S-expressions, an extremely simple form of structured data representation that is nevertheless fundamental to the development of Lisp syntactic extensions. By adopting a more conventional syntax, the Java language placed itself in a difficult position in regard to user-defined syntax extensions. In spite of the many efforts to provide mechanisms for such extensions, they continue to be more difficult to use than S-expressionbased ones. In this paper, we will describe the use of the S-expression syntax in a Java code generation environment. By providing an Sexpression based program representation for Java source code, we are able to reuse and extend Lisp macro-expansion techniques to significantly simplify the construction of Java programs.