Efficient Compilation of Control Effects (ECCE)

The history of programming language design and implementation is to a significant degree the history of control structures. The last decade has seen a new proliferation of advanced control structures, such as async/await, generators, coroutines, and fibers. These new control structures promise improved program structure, including the avoidance of “callback hell”, and generally a higher level of abstraction.

However, the way such control structures are implemented today is highly unsatisfactory. They are often hard-coded into a language, meaning that they are not user-definable; they are not composable, meaning that programs using different abstractions cannot be combined in one project; or implementations for one control abstraction cannot be reused to implement similar control abstractions.

To resolve these limitations, we embrace effect handlers as a high-level control abstraction. Backed by a strong theoretical foundation and a static type-and-effect system, effect handlers encourage a modular definition of control abstractions as user-definable libraries and naturally allow users to compose these libraries in one program. As of today, the abstraction of effect handlers comes with a cost in performance. The goal of the ECCE project (Efficient Compilation of Control Effects) is to remove these costs and provide control-flow abstraction without regret.

Specifically, we aim to establish a research programme to achieve novel compile-time and just-in-time optimizations for effect handlers, accompanied by both a theoretical framework to reason about correctness and costs and implementations for realistic languages. Efficient effect handlers will enable programmers to develop many general-purpose and domain-specific control-flow constructs without sacrificing performance.

Results