DEV Community: xavier2code

Daliy.rust day 3

xavier2code — Tue, 05 Nov 2024 02:36:22 +0000

fn main() {
    // In general, the `{}` will be automatically replaced with any
    // arguments. These will be stringified.
    println!("{} days", 31);

    // Positional arguments can be used. Specifying an integer inside `{}`
    // determines which additional argument will be replaced. Arguments start
    // at 0 immediately after the format string.
    println!("{0}, this is {1}. {1}, this is {0}", "Alice", "Bob");

    // As can named arguments.
    println!("{subject} {verb} {object}",
             object="the lazy dog",
             subject="the quick brown fox",
             verb="jumps over");

    // Different formatting can be invoked by specifying the format character
    // after a `:`.
    println!("Base 10:               {}",   69420); // 69420
    println!("Base 2 (binary):       {:b}", 69420); // 10000111100101100
    println!("Base 8 (octal):        {:o}", 69420); // 207454
    println!("Base 16 (hexadecimal): {:x}", 69420); // 10f2c

    // You can right-justify text with a specified width. This will
    // output "    1". (Four white spaces and a "1", for a total width of 5.)
    println!("{number:>5}", number=1);

    // You can pad numbers with extra zeroes,
    println!("{number:0>5}", number=1); // 00001
    // and left-adjust by flipping the sign. This will output "10000".
    println!("{number:0<5}", number=1); // 10000

    // You can use named arguments in the format specifier by appending a `$`.
    println!("{number:0>width$}", number=1, width=5);

    // Rust even checks to make sure the correct number of arguments are used.
    println!("My name is {0}, {1} {0}", "Bond");
    // FIXME ^ Add the missing argument: "James"

    // Only types that implement fmt::Display can be formatted with `{}`. User-
    // defined types do not implement fmt::Display by default.

    #[allow(dead_code)] // disable `dead_code` which warn against unused module
    struct Structure(i32);

    // This will not compile because `Structure` does not implement
    // fmt::Display.
    // println!("This struct `{}` won't print...", Structure(3));
    // TODO ^ Try uncommenting this line

    // For Rust 1.58 and above, you can directly capture the argument from a
    // surrounding variable. Just like the above, this will output
    // "    1", 4 white spaces and a "1".
    let number: f64 = 1.0;
    let width: usize = 5;
    println!("{number:>width$}");
}

Daily.rust day 2

xavier2code — Tue, 05 Nov 2024 02:34:54 +0000

fn main() {
    // This is an example of a line comment.
    // There are two slashes at the beginning of the line.
    // And nothing written after these will be read by the compiler.

    // println!("Hello, world!");

    // Run it. See? Now try deleting the two slashes, and run it again.

    /*
     * This is another type of comment, a block comment. In general,
     * line comments are the recommended comment style. But block comments
     * are extremely useful for temporarily disabling chunks of code.
     * /* Block comments can be /* nested, */ */ so it takes only a few
     * keystrokes to comment out everything in this main() function.
     * /*/*/* Try it yourself! */*/*/
     */

    /*
    Note: The previous column of `*` was entirely for style. There's
    no actual need for it.
    */

    // You can manipulate expressions more easily with block comments
    // than with line comments. Try deleting the comment delimiters
    // to change the result:
    let x = 5 + /* 90 + */ 5;
    println!("Is `x` 10 or 100? x = {}", x);
}

Daily.rust day 1

xavier2code — Tue, 05 Nov 2024 02:33:12 +0000

// This is a comment, and is ignored by the compiler.
// You can test this code by clicking the "Run" button over there ->
// or if you prefer to use your keyboard, you can use the "Ctrl + Enter"
// shortcut.

// This code is editable, feel free to hack it!
// You can always return to the original code by clicking the "Reset" button ->

// This is the main function.
fn main() {
    // Statements here are executed when the compiled binary is called.

    // Print text to the console.
    println!("Hello World!");
}

Ownership

xavier2code — Mon, 28 Oct 2024 02:54:09 +0000

Ownership is Rust's most unique feature and has deep implications for the rest of the language. it enables Rust to make memory safety guarantees without needing a garbage collector.

Ownership is a set of rules that govern how a Rust program manages memory.

Each value in Rust has an owner.
There can only be one owner at a time.
When the owner goes out of scope, the value will be dropped.