[swift-evolution] Representation of natural numbers with a distinct type

[David Turnbull]

On Thu, Feb 4, 2016 at 3:48 AM, James Froggatt <conductator at ntlworld.com>
wrote:

> CGSize represents vectors *and* sizes? And an explicit ‘normalisation’ (a
> non-negative safety check) must be performed to work with CGSize as a size?
> This sounds awfully like a lack of type safety.
>

That's an invariant. Enforcing y>=x with a type system is just as hard as
the halting problem.

-david
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