Comments

Comments are C-style, including /* … */ pairs for block comments and // for comments to the end of the line.

Block comments can be nested.

let /* intruder comment */ name = "Bob";

// This is a very important one-line comment

/* This comment spans
   multiple lines, so it
   only makes sense that
   it is even more important */

/* Fear not, Rhai satisfies all nesting needs with nested comments:
   /*/*/*/*/**/*/*/*/*/
*/

Doc-Comments

Comments starting with /// (three slashes) or /** (two asterisks) are doc-comments.

Doc-comments can only appear in front of function definitions, not any other elements.

/// This is a valid one-line doc-comment
fn foo() {}

/** This is a
 ** valid block
 ** doc-comment
 **/
fn bar(x) {
   /// Syntax error: this doc-comment is invalid
   x + 1
}

/** Syntax error: this doc-comment is invalid */
let x = 42;

/// Syntax error: this doc-comment is also invalid
{
   let x = 42;
}

///////////////////////////////  <- this is not a doc-comment
// This is not a doc-comment //  <- this is not a doc-comment
///////////////////////////////  <- this is not a doc-comment

// However, watch out for comment lines starting with '///'

//////////////////////////////////////////  <- this is not a doc-comment
/// This, however, IS a doc-comment!!! ///  <- doc-comment!
//////////////////////////////////////////  <- this is not a doc-comment

/****************************************
 *                                      *
 * This is also not a doc-comment block *
 * so we don't have to put this in      *
 * front of a function.                 *
 *                                      *
 ****************************************/

Module Documentation

Comment lines starting with //! make up the module documentation.

They are used to document the containing module – or for a Rhai script file, to document the file itself.

//! Documentation for this script file.
//! This script is used to calculate something and display the result.

fn calculate(x) {
   ...
}

fn display(msg) {
   //! Module documentation can be placed anywhere within the file.
   ...
}

//! All module documentation lines will be collected into a single block.

For the example above, the module documentation block is:

//! Documentation for this script file.
//! This script is used to calculate something and display the result.
//! Module documentation can be placed anywhere within the file.
//! All module documentation lines will be collected into a single block.