SIMPLE OBJECTS FOR STANDARD ML

We propose a new approach to adding objects to Standard ML (SML) based on explicit declarations of object types, object constructors, and su btyping relationships, with a generalization of the SML case statement to a ''typecase'' on object types. The language, called Object ML (OM L), has a type system that conservatively extends the SML type system, preserves sound static typing, and permits type inference. The type s ystem sacrifices some of the expressiveness found in recently proposed schemes, but has the virtue of simplicity. We give examples of how fe atures found in other object-oriented languages can be emulated in OML , discuss the formal properties of OML, and describe some implementati on issues.