We present Éclat, a functional language tailored for programming hardware applications interacting in real time with physical devices while running computations having long response times.

Éclat targets a hardware description language for synthesizing hardware applications on Field Programmable Gate Arrays (FPGAs).

We explore the programming possibilities of this approach by implementing, in Éclat, a virtual machine (VM) for the high-level multi-paradigm language OCaml. This VM implementation comprises a bytecode interpreter and a runtime system with automatic memory management. The runtime is customizable by the programmer, by defining Éclat external functions (i.e., hardware accelerators).

The VM itself is an Éclat function that can be called from reactive applications (programmed in Éclat) to execute complex computations (programmed in OCaml).