implementation of strsplit from rust lifetime annotations video. i paused video pretty early and made a more robust implementation
$ cargo test// base case
let haystack = "a b c d e";
let letters = StrSplit::new(haystack, " ").collect::<Vec<_>>();
assert_eq!(letters, vec!["a", "b", "c", "d", "e"]);
// long delimiter
let haystack = "barfoobaz";
let letters = StrSplit::new(haystack, "foo").collect::<Vec<_>>();
assert_eq!(letters, vec!["bar", "baz"]);
// empty haystack
let haystack = "";
let letters = StrSplit::new(haystack, " ").collect::<Vec<_>>();
assert_eq!(letters, vec![] as Vec<&str>);
// delimiter not found
let haystack = "foo bar";
let letters = StrSplit::new(haystack, "baz").collect::<Vec<_>>();
assert_eq!(letters, vec!["foo bar"]);
// empty delimiter returns each character as str
let haystack = "abcd";
let letters = StrSplit::new(haystack, "").collect::<Vec<_>>();
assert_eq!(letters, vec!["a", "b", "c", "d"]);