Find The Index Of A Substring Within A String In Rust

In the world of programming, finding the index of a substring within a string is a common requirement that programmers face often. This article will provide you with an easy understanding of finding the string index in Rust.

Code snippet: Finding the Index of a Substring within a String in Rust

    let main_string = "Hello, Rust programmers!";
    let sub_string = "Rust";

    match main_string.find(sub_string) {
        Some(index_of_substring) => println!("Found {} at index {}", sub_string, index_of_substring),
        None => println!("{} not found in '{}'", sub_string, main_string),
    }

Code Explanation: Finding the Index of a Substring within a String in Rust

The above example uses Rust’s in-built find() function to locate the index of a substring within a string. The code is self-explanatory, yet it is always beneficial to understand it at a deeper level. Let’s break it down:

1. let main_string = "Hello, Rust programmers!";: This line sets up a string called “main_string”. This is the string that will be searched.

2. let sub_string = "Rust";: This line sets up the ‘sub_string’. This is the string that we want to find within the ‘main_string’.

3. match main_string.find(sub_string) {: The find() function is called on ‘main_string’ and ‘sub_string’ is passed as a parameter. The find() function returns an Option that contains the start index of the ‘sub_string’. If the ‘sub_string’ is not found, it returns ‘None’. Using ‘match’ allows us to handle both of these outcomes.

4. Some(index_of_substring) => println!("Found {} at index {}", sub_string, index_of_substring),: If the ‘sub_string’ is found within the ‘main_string’, the returned value will match ‘Some(index_of_substring)‘. Then it will print a message indicating the ‘sub_string’ and the index where it was found.

5. None => println!("{} not found in '{}'", sub_string, main_string),: If the ‘sub_string’ is not found within the ‘main_string’, it will match ‘None’ and print a message saying that the ‘sub_string’ was not found in the ‘main_string’.