# nanval [![Crates.io](https://img.shields.io/crates/v/nanval?style=flat)](https://crates.io/crates/nanval) [![Docs.rs](https://docs.rs/nanval/badge.svg)](https://docs.rs/nanval) [![GitHub](https://img.shields.io/github/languages/top/Longor1996/nanval)](https://github.com/Longor1996/nanval) [![LOC](https://tokei.rs/b1/github/Longor1996/nanval)](https://github.com/Longor1996/nanval) A `no_std`, zero-dependency crate for the creation and handling of NaN-tagged 64-bit floating-point values. > Inspired by [this article](https://sean.cm/a/nan-boxing) and [this crate](https://github.com/Marwes/nanbox). ## How does this work? When a 64-bit floating-point number is set to `NaN`/`0x7FF8000000000000`, its bits are as follows: ```text s111 1111 1111 1qxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx ^ ^\____________________________________________________________/ | | ^ | Sign Bit | Quiet Bit | Data Bits ``` As long as the data bits aren't all set to `0`, indicating the original/sentinel `NaN` value, they can be literally anything else! This gives us 50 bits to mess with/use as we please... ### UInts / Unsigned Integers > Look at the module [`crate::uint`] for this. **TODO:** Add explanation. ### Cells / Pointers > Look at the module [`crate::cell`] for this. Since it doesn't matter what the sign-bit `s` is set to, we can use it as a flag/marker that indicates that the value is some kind of `cell` or `ptr`. Combine this with the fact that basically all x64-platforms only use the lower 48 or 50 bits for addressing (ignoring CHERI shenanigans), we are left with 3 bits (that includes the 'quiet' bit) to store some kind of type-tag for the cell; look at the [`crate::cell::CellTag`]. ## References - - - -