> Rust has its uint-thats-not-zero

Why do we need to single out a specific value. It would be way better if we also could use uint-without-5-and-42. What I would wish for is type attributes that really belong to the type.

    typedef unsigned int __attribute__ ((constraint (X != 5 && X != 42))) my_type;

▲ int_19h 2 days ago | parent | next [-]

Proper union types would get you there. If you have them, then each specific integer constant is basically its own type, and e.g. uint8 is just (0|1|2|...|255). So long as your type algebra has an operator that excludes one of the variants from the union to produce a new one, it's trivial to exclude whatever, and it's still easy for the compiler to reason about such types and to provide syntactic sugar for them like 0..255 etc.

▲ steveklabnik 2 days ago | parent | prev [-]

Those are the unstable attributes that your sibling is talking about.

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1718627440 2 days ago | parent [-]

Yeah of course I can put what I want in my toy compiler. My statement was about standard C. I think that's what Contracts really are and hope this will be included in C.

	▲	steveklabnik 2 days ago \| parent [-]
		Oh sure, I wouldn’t call rustc a “toy compiler” but yeah, they’d be cool in C as well.