Writing a Game Boy Emulator in OCaml

Would anyone here assert that there's any particular programming language that's better for writing emulators, virtual machines, bytecode interpreters, etc?

Where, when I say "better", I'm not so much talking about getting results that are particularly efficient/performant; nor in making fewer implementation errors... but more in terms of the experience of implementing an emulator in this particular language, being more rewarding, intuitive, and/or teaching you more about both emulators and the language.

I ask because I know that this sort of language exists in other domains. Erlang, for example, is particularly rewarding to implement a "soft-realtime nine-nines-of-uptime distributed system" in. The language, its execution semantics, its runtime, and its core libraries, were all co-designed to address this particular problem domain. Using Erlang "for what it's for" can thus teach you a lot about distributed systems (due to the language/runtime/etc guiding your hand toward its own idiomatic answers to distributed-systems problems — which usually are "best practice" solutions in theory as well); and can lead you to a much-deeper understanding of Erlang (exploring all its corners, discovering all the places where the language designers considered the problems you'd be having and set you up for success) than you'd get by trying to use it to solve problems in some other domain.

Is there a language like that... but where the "problem domain" that the language's designers were targeting, was "describing machines in code"?

Haskell excels at DSLs and the sort of data manipulation needed in compilers. OCaml, Lisp, and really any language with support for ADTs and such things do the trick as well. You can even try hard with modern C++ and variant types and such, but it won't be as pretty.

Of course, if you actually want to run games on the emulator, C or C++ is where the game is. I suppose Rust would work too, but I can't speak much for its low-level memory manipulation.

Haskell and OCaml are excellent for compilers, because - as you suggest - you end up building, walking, and transforming tree data structures where sum types are really useful. Lisp is an odd suggestion there, as it doesn’t really have any built-in support for this sort of thing.

At any rate, that’s not really the case when building an emulator or bytecode interpreter. And Haskell ends up being mostly a liability here, because most work is just going to be imperatively modifying your virtual machine’s state.