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by tialaramex
646 days ago
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> This is often implemented with a zero pointer indicating None, but the user doesn't see that. The Guaranteed Niche Optimisation is, as its name suggests, guaranteed by the Rust language. That is, Option<&T> is guaranteed to be the same size as &T. The choice for the niche to be the all-zero bit representation is in some sense arbitrary but I believe it is a written promise too. |
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