A Parallel Functional Language with First-Class Continuations. Programming Style and Semantics

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Description/Abstract

We present an operational semantics for a functional language with first-class continuations and transparent constructs for parallelism fork and pcall. The sequential semantics of programs with first-class continuations is preserved when parallel evaluation is allowed, by verifying whether some expressions have returned a value before applying a continuation. These expressions are the ones that are evaluated before this continuation is applied in a left-to-right sequential order. An implementation is proposed using a notion of higher-order continuation that we call metacontinuation. This semantics is costless when first-class continuations are not used. Several programs also illustrate the programming style that can be adopted in such a language.