Lambda the Ultimate

Abdulaziz Ghuloum and R. Kent Dybvig, Implicit Phasing for R6RS Libraries, Proc. ICFP 2007.

The forthcoming Revised Report on Scheme differs from previous reports in that the language it describes is structured as a set of libraries. It also provides a syntax for defining new portable libraries. The same library may export both procedure and hygienic macro definitions, which allows procedures and syntax to be freely intermixed, hidden, and exported.

This paper describes the design and implementation of a portable version of R6RS libraries that expands libraries into a core language compatible with existing R5RS implementations. Our implementation is characterized by its use of inference to determine when the bindings of an imported library are needed, e.g., run time or compile time, relieving programmers of the burden of declaring usage requirements explicitly.

R6RS leaves it up to implementations whether import statements need to explicitly state the meta-level into which bindings should be placed. The authors argue for letting the implementation automatically figure out the required meta-levels, and present an implementation-oriented description of how to do so, that they implemented portably. The paper also includes a well-written and detailed introduction to the issues involved, and since they want the community to adopt their solution, they seem to have worked extra hard to produce a convincing paper ;).

(via vieiro)