Writing distributed applications is hard, as the programmer needs to describe the communication protocol between the different endpoints. If this is not done correctly, we can introduce bugs such as deadlocks and data races. Tierless and choreographic programming models aim to make this easier by describing the interactions of every endpoint in a single compilation unit. When such a program is compiled, ideally, a single endpoint is projected and the code for the other endpoints is removed. This leads to smaller binaries with fewer dependencies, and is called program partitioning. In this pearl, we show how we can use rewrite rules and specialisation to get GHC to partition our Haskell programs (almost) for free, if they are written using the Haste App or HasChor framework. As an example of why partitioning is useful, we show how an example application can be more easily built and deployed after being partitioned.

Trusted Execution Environments (TEEs) are hardware enforced memory isolation units, emerging as a pivotal security solution for security-critical applications. TEEs, like Intel SGX and ARM TrustZone, allow the isolation of confidential code and data within an untrusted host environment, such as the cloud and IoT. Despite strong security guarantees, TEE adoption has been hindered by an awkward programming model. This model requires manual application partitioning and the use of error-prone, memory-unsafe, and potentially information-leaking low-level C/C++ libraries.

We describe the development of a new programming language Scoria and its compiler. Scoria is a high-level reactive real-time language based on the sparse synchronous model (SSM), designed to produce time- and power-efficient low-level C code that can run on small IoT devices. While the compiler is not yet in a state where it is meaningful to measure power usage, we carefully profile the timing behaviour and identify bottlenecks that can improve performance. The language and compiler are implemented as an Embedded Domain-Specific Language (EDSL) on top of Haskell.

Programming microcontrollers involves low level interfacing with hardware and peripherals that are concurrent and reactive. Such programs are typically written in a mixture of C and assembly using concurrent language extensions (like FreeRTOS tasks and semaphores), resulting in unsafe, callback-driven, error-prone and difficult-to-maintain code.