A Separate Compilation Extension to Standard ML (Revised and Expanded)

We present an extension to Standard ML, called SMLSC, to support separate compilation. The system gives meaning to individual program fragments, called units. Units may depend on one another in a way specified by the programmer. A dependency may be mediated by an interface (the type of a unit); if so, the units can be compiled separately. Otherwise, they must be compiled in sequence. We also propose a methodology for programming in SMLSC that reflects code development practice and avoids syntactic repetition of interfaces. The language is given a formal semantics, and we argue that this semantics is implementable in a variety of compilers.