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

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Description/Abstract

We define a partial continuation as the difference of two continuations. 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 prefixal extent that characterises the time during which a partial continuation can be reified. 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.