Rust String

05 Dec 2022 . category: . Comments
#rust

In Rust, strings are sequences of Unicode characters and are represented by the String type. The String type is a growable, mutable, owned string type, and is used for representing and manipulating strings in Rust. It is dynamic heap string type and stored as vector of bytes(Vec<u8>).

In addition to the String type, Rust also has a fixed-sized string type called str, which is a slice that refers to a sequence of Unicode characters. The str type is immutable and cannot be modified, but it is typically used as the argument and return type for string-related functions in Rust. The &str is called slice (&[8]) that points to valid UTF-8 sequence, and used to view into a String….

**&str can be called a “string slice” or “slice” **

Example:

fn main(){
    // Declare a mutable String
    let mut s = String::new();

    // Append a string slice to the String
    s.push_str("Hello, ");

    // Append a string literal to the String
    s.push('w');
    s.push('o');
    s.push('r');
    s.push('l');
    s.push('d');

    // Convert the String to a string slice
    let s_slice: &str = &s;

    // Print the string slice
    println!("{}", s_slice);
}

Results:

Hello, world

Here is an example.

fn main() {
    // (all the type annotations are superfluous)
    // A reference to a string allocated in read only memory
    let pangram: &'static str = "the quick brown fox jumps over the lazy dog";
    println!("Pangram: {}", pangram);

    // Iterate over words in reverse, no new string is allocated
    println!("Words in reverse");
    for word in pangram.split_whitespace().rev() {
        println!("> {}", word);
    }

    // Copy chars into a vector, sort and remove duplicates
    let mut chars: Vec<char> = pangram.chars().collect();
    chars.sort();
    chars.dedup();

    // Create an empty and growable `String`
    let mut string = String::new();
    for c in chars {
        // Insert a char at the end of string
        string.push(c);
        // Insert a string at the end of string
        string.push_str(", ");
    }

    // The trimmed string is a slice to the original string, hence no new
    // allocation is performed
    let chars_to_trim: &[char] = &[' ', ','];
    let trimmed_str: &str = string.trim_matches(chars_to_trim);
    println!("Used characters: {}", trimmed_str);

    // Heap allocate a string
    let alice = String::from("I like dogs");
    // Allocate new memory and store the modified string there
    let bob: String = alice.replace("dog", "cat");

    println!("Alice says: {}", alice);
    println!("Bob says: {}", bob);
}

Sources

Resources

Rust-by-example about strings

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Rust String

05 Dec 2022 . category: . Comments #rust

Resources

05 Dec 2022 . category: . Comments
#rust