Comments

Comments are a way to add notes or document your code. They are ignored by the compiler and don't result in the Move bytecode. You can use comments to explain what your code does, to add notes to yourself or other developers, to temporarily remove a part of your code, or to generate documentation. There are three types of comments in Move: line comment, block comment, and doc comment.

Line comment

You can use double slash // to comment out the rest of the line. Everything after // will be ignored by the compiler.

module book::comments_line;

// let's add a note to everything!
fun some_function_with_numbers() {
    let a = 10;
    // let b = 10 this line is commented and won't be executed
    let b = 5; // here comment is placed after code
    a + b; // result is 15, not 10!
}

Block comment

Block comments are used to comment out a block of code. They start with /* and end with */. Everything between /* and */ will be ignored by the compiler. You can use block comments to comment out a single line or multiple lines. You can even use them to comment out a part of a line.

module book::comments_block;

fun /* you can comment everywhere */ go_wild() {
    /* here
        there
        everywhere */ let a = 10;
    let b = /* even here */ 10; /* and again */
    a + b;
}
/* you can use it to remove certain expressions or definitions
fun empty_commented_out() {

}
*/

This example is a bit extreme, but it shows how you can use block comments to comment out a part of a line.

Doc comment

Documentation comments are special comments that are used to generate documentation for your code. They are similar to block comments, but they start with three slashes /// and are placed before the definition of the item they document.

/// Module has documentation!
module book::comments_doc;

/// This is a 0x0 address constant!
const AN_ADDRESS: address = @0x0;

/// This is a struct!
public struct AStruct {
    /// This is a field of a struct!
    a_field: u8,
}

/// This function does something!
/// And it's documented!
fun do_something() {}