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Comment by fpoling | Hacker News Reader

Arbitrary subranges of int types were available in Ada for over 40 years via static enforcement via Spark and compilers were able to optimize them nicely.

For a system language I wish Rust would support such things rather than coming with NonZero hacks.

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This is called "pattern types" in Rust land, as your parent mentioned, and is exactly the kind of work being talked about.

NonZero isn't a hack: it's an example of a common pattern. If pattern types were available today, you'd still want NonZero, as an example of a pretty standard pattern.

The idea is, as always: prove out the specific version, then generalize.

Can it do holes like this?

  (typep 3 '(or (integer 0 10) (integer 50 100)));; => T

You can use a "subtype predicate" for this: https://learn.adacore.com/courses/Ada_For_The_CPP_Java_Devel...

Might be less efficient, no? At least in CL (https://www.lispworks.com/documentation/HyperSpec/Body/t_sat...) this is the case, that static type analysis isn't clever enough to work with predicate based types.

I don't know enough about the details to speak to it.

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