Partial Continuations as the Difference of Continuations - A Duumvirate of Control Operators

We de ne a partial continuation as the di erence of two continua tions We exhibit in a single framework several design choices and their impact on semantics The ability of partial continuations to manipulate stack frames blurs the nature of dynamic extent therefore we introduce a new concept of pre xal extent that characterises the time during which a partial continu ation can be rei ed We propose two equivalent formal semantics for partial continuations a context rewriting system and a cps translation Two new and realistic examples illustrate both the interest of partial continuations and the expressiveness of our choices