A lot of the tooling speed comes from a couple places:
1. The compiler optimizations being applied to code
- Things like GADT's are able to be allocated very efficiently
- Can generate code that doesn't box at runtime (smash it into a pointer is done as well)
- Pointers are word-aligned
2. The OCaml runtime
- No JIT
- No warmup
- Can emit native code
3. The HM type system
- Typecheckers for HM are really simple [1]
This simplicity + the features of the compiler combine to make the OCaml compiler very fast, and very easy to write one (some undergrad CS classes do), and developer-time tenable to make both happen.
1. The compiler optimizations being applied to code - Things like GADT's are able to be allocated very efficiently - Can generate code that doesn't box at runtime (smash it into a pointer is done as well) - Pointers are word-aligned
2. The OCaml runtime - No JIT - No warmup - Can emit native code
3. The HM type system - Typecheckers for HM are really simple [1]
[1] https://en.wikipedia.org/wiki/Hindley%E2%80%93Milner_type_sy...
This simplicity + the features of the compiler combine to make the OCaml compiler very fast, and very easy to write one (some undergrad CS classes do), and developer-time tenable to make both happen.