锈书
锈书的例子。
值得注意的注意事项：
Chp3-Chp5：代码符号中保留关键字名称的引用名称； 例如，
let r#len = 99; // lets us use `len` as a var name even though it's a reserved keyword
// Slicing
&some_string[..9] // Turns `String` into slice from `0` to `9`
&some_string[9..] // "" "" "" from 9 to length of String
&some_string[..] // Turns `String` into slice
some_string.as_str() // Turns `String` into slice
