Comment by umanwizard

Indeed this isn't anywhere in the Rust standard library, but there is `ordered_float::NotNan`: https://docs.rs/ordered-float/latest/ordered_float/struct.No... .

Unfortunately, Rust doesn't seem to be smart enough to represent `Option<NotNan<f64>>` in 8 bytes, even though in theory it should be possible (it does the analogous thing with `Option<NonZero<u64>>`).

This thread is discussing the possibility of adding such an optimization: https://internals.rust-lang.org/t/add-float-types-with-niche...