Crate midstring

This rust crate is for creating a string between two other strings, that is lexicographically halfway between them.

// "aaa" |
//       | -> creates "aan"
// "aaz" |

This is useful for re-ordering items in the database with only one update. Get the left and right key strings (that is used for ordering), then create the new key string with mid_string() function. Then assign this key string to the new item that is placed in between the previous two items. If you sort by this key, it should be ordered correctly.

Important! For now, this works only for lower case English ascii characters: [a ~ z]. Other characters will result in unpredictable behaviour.

This library is based on the answer provided by “m69” to the following stackoverflow.com question:

https://stackoverflow.com/questions/38923376/return-a-new-string-that-sorts-between-two-given-strings

Question: Return a new string that sorts between two given strings

Answer provided by “m69 snarky and unwelcoming”: https://stackoverflow.com/a/38927158/1762976

Examples

use midstring::mid_string;

// create new strings from empty strings
println!("_, i => {}", mid_string("", "i")); // -> e
println!("_, b => {}", mid_string("", "b")); // -> an
println!("_, _ => {}", mid_string("", "")); // -> n

assert_eq!(mid_string("", "i"), "e");
assert_eq!(mid_string("", "b"), "an");
assert_eq!(mid_string("", ""), "n");

// create new strings between other strings
assert_eq!(mid_string("aaa", "aaz"), "aan");
assert_eq!(mid_string("abc", "abcab"), "abcaan");

assert_eq!(mid_string(&String::from("abcde"), "abchi"), String::from("abcf"));

let left = String::from("abc");
let right = "abcab".to_string();
let should_be = String::from("abcaan");
assert_eq!(mid_string(&left, &right), should_be);

Functions

mid_string

Create a string that is lexicographically halfway between the left and right strings