String slicing is the process of extracting a part of a string from the main string. In Rust, string slicing can be done using the [] operator with a range syntax. The range syntax is [start_index..end_index], where start_index is the first position in the slice and end_index is one more than the last position in the slice.
For example, to slice the first four bytes of the string "Здравствуйте", you would use the following code:
let hello = "Здравствуйте";
let s = &hello[0..4];
The variable s will be a &str that contains the first four bytes of the string, which is "Зд".
It is important to note that string slicing in Rust is byte-based, not character-based. This means that if you slice a string that contains multi-byte characters, you may not get the expected result. For example, if you slice the string "Здравствуйте" at the byte index 1, you will get the string "З", which is only half of the character "З".
To avoid this problem, you should use ranges to create string slices with caution. If you need to slice a string at a character boundary, you can use the char_indices() method to iterate over the characters in the string and find the starting and ending indices of the slice you want.
Here is an example of how to slice a string at a character boundary:
let hello = "Здравствуйте";
// Find the index of the first space character.
let first_space_index = hello.char_indices().find(|(_, c)| *c == ' ').unwrap().0;
// Slice the string from the beginning to the first space character.
let first_word = &hello[0..first_space_index];
The variable first_word will be a &str that contains the first word in the string, which is "Зд".
