The spineless G-machine

Abstract

Recent developments in functional language implementations have resulted in the G-machine, a programmed graph-reduction machine. Taking this as a basis, we introduce an optimised method of performing graph reduction, which does not need to build the spine of the expression being reduced. This Spineless G-machine only updates shared expressions, and then only when they have been reduced to weak head normal form. It is thus more efficient than the standard method of performing graph reduction.