The LISCOM version of the AI group PDP/6 LISP compiler is a descendant of the original Greenblatt-Nelson compiler, and is a friendly sibling to the COMPLR version maintained by Jon L. White. The compiler operates in two passes to translate LISP code into LAP code. The first pass performs a general study of the S-expression function definition which is to be compiled, producing as output a modified S-expression and various tables attached to free variables. The second pass does the actual compilation (generation of assembly code), making use of the transformations performed and the information gathered by the first pass. The LISCOM version of the compiler is being used as a vehicle for the implementation of "fast arithmetic" in LISP. This work is being done under the auspices of the MATHLAB project of the AI Laboratory. The early stages of the compiler implementation were handled by W. Diffie, and the work has been continued by the present author.
