Effect handlers provide a structured means for implementing user-defined, composable, and customisable computational effects, ranging from exceptions to generators to lightweight threads. We introduce libseff , a novel effect handlers library for C, based on coroutines. Whereas prior effect handler libraries for C are intended primarily as compilation targets, libseff is intended to be used directly from C programs. As such, the design of libseff parts ways from traditional effect handler implementations, both by using mutable coroutines as the main representation of pending computations, and by avoiding closures as handlers by way of reified effects. We show that the performance of libseff is competitive across a range of platforms and benchmarks.

The lambda-PRK-calculus is a typed lambda-calculus that exploits the duality between the notions of proof and refutation to provide a computational interpretation for classical propositional logic. In this work, we extend lambda-PRK to encompass classical second-order logic, by incorporating parametric polymorphism and existential types. The system is shown to enjoy good computational properties, such as type preservation, confluence, and strong normalization, which is established by means of a reducibility argument. We identify a syntactic restriction on proofs that characterizes exactly the intuitionistic fragment of second-order lambda-PRK, and we study canonicity results.

Union and intersection types are a staple of gradually typed languages such as TypeScript. While it's long been recognized that union and intersection types are difficult to verify statically, it may appear at first that the dynamic part of gradual typing is actually pretty simple.