An extension of ML with continuation primitives similar to those found in
Scheme is considered.  A number of alternative type systems are discussed, and
several programming examples are given.  A continuation-based operational
semantics is defined for a small, purely functional, language, and
the soundness of the Damas-Milner polymorphic type assignment system with
respect to this semantics is proved.  The full Damas-Milner type system is
shown to be unsound in the presence of first-class continuations.
Restrictions on polymorphism similar to those introduced in connection with
reference types are shown to suffice for soundness.