Crate base79[−][src]
Expand description
Textual representation of and utility functions for base-79 fractional numbers with arbitrary precision.
It can only represent numbers between 0 and 1, exclusive. The leading 0. is omitted.
Heavily inspired by this article.
Why 79?
- UTF-8 can encode ASCII with 1 byte per character.
- ASCII has 95 printable characters in total, but some of them will seem really odd if they were to surface to end-users. We could take just the alphanumeric characters (62), but that seems too limited. We take the middle 79 to exclude some of the characters on the ends, such as the space, which isn’t very conspicuous when reading, and quote marks, which often need escaping.
Example
use base79::Base79; use std::str::FromStr; let n1 = Base79::mid(); assert_eq!(n1.to_string(), "R"); assert_eq!(n1.raw_digits(), vec![39]); assert_eq!(39 + 1 + 39, 79); // How we got 39. let n2 = Base79::avg_with_zero(&n1); assert_eq!(n2.to_string(), ">"); assert_eq!(n2.raw_digits(), vec![19]); assert_eq!(19.5*2.0 + 1.0 + 19.5*2.0, 79.0); // How we got 19. let n3 = Base79::avg_with_one(&n1); assert_eq!(n3.to_string(), "f"); assert_eq!(n3.raw_digits(), vec![59]); let n4 = Base79::avg(&n1, &n2); assert_eq!(n4.to_string(), "H"); assert_eq!(n4.raw_digits(), vec![29]); let n5 = Base79::from_str("s?Q^Z").unwrap(); assert_eq!(n5.raw_digits(), vec![72, 20, 38, 51, 47]);
Why is avg imprecise?
One of main considerations of this representation is storage efficiency of fractional index. So it is better to have a little imprecise, shorter string, than perfectly precise, longer string.
Of course, the result is deterministic, i.e., if the input is same, the output will always be same.