A Scheme-to-Java Translator with Soft Typing

This paper presents a compiler that translates Scheme code into the Java language. The programming language Scheme is known to be highly expressive and safe. By translating Scheme into Java, one can benefit from such features of Scheme as well as the portability of Java. Our compiler implements dynamic type checking in Scheme via down-casting in Java by mapping each Scheme value to a Java Object. However, naively doing so requires dynamic class checking in Java for every primitive operation in Scheme and thereby incurs much overhead. We reduce this overhead of runtime type checking by exploiting partial static type information obtained through soft typing. This method achieves about 200–700% speedup in micro benchmarks and 67% for a ray tracing program. Thus, our compiler combines the expressiveness and safety of Scheme with the portability of Java without much loss of efficiency.