Poly/ML is a Standard ML implementation that originated in the experimental language Poly. Since version 4.0 it fully conforms to the ML97 standard, a fact that sets it apart from other compilers that rely on extensions. The project’s history and milestones are archived in the official documentation.

Poly/ML delivers a fast compiler and a suite of extensions that keep the language lean. The thread library offers a lightweight Posix‑style API and enables parallel execution; the garbage collector runs in parallel as well. The foreign‑function interface lets static and dynamic C libraries be linked and accessed as Poly/ML functions, illustrated in the sample code. A symbolic debugger is available on Windows, and the mailing list provides ongoing support.

Hardware support covers 32‑ and 64‑bit i386 and 64‑bit ARM; other architectures run through a byte‑code interpreter. Installation is straightforward, with download links and build instructions on the official site. The mailing list remains the primary channel for community interaction and troubleshooting.

Poly/ML’s strict adherence to the Standard ML specification, combined with thread‑level concurrency and a stable foreign‑function interface, makes it a practical choice for large projects such as HOL that demand reproducible semantics and efficient parallelism.