Sigma16 is an instruction set architecture with software tools, including an assembler, emulator, and a digital circuit.
Hydra is a functional computer hardware description language for specifying digital circuits. Hydra uses Haskell notation and is implemented by embedding in Haskell. The language provides tools for specifying synchronous circuits from the level of logic gates to register transfer level to subsystem design. The language semantics is equivalent to the actual circuit semantics, so you can simulate a circuit by executing the Hydra specification.