Core Lib Documentation: box module (#6651)

Co-authored-by: Mathieu <[email protected]>

corelib/src/box.cairo

@@ -1,6 +1,44 @@
-/// A Box is a type that points to a wrapped value.
-///
-/// Allows for cheap moving around of the value, as its size is small, and may wrap a large size.
+//! `Box<T>` is a smart pointer that allows for:
+//!
+//! * Storing values of arbitrary size while maintaining a fixed-size pointer
+//! * Enabling recursive types that would otherwise have infinite size
+//! * Moving large data structures efficiently by passing pointers instead of copying values
+//!
+//! # Examples
+//!
+//! Creating a new box with [`BoxTrait::new`]:
+//!
+//! ```
+//! let boxed = BoxTrait::new(42);
+//! let unboxed = boxed.unbox();
+//! ```
+//!
+//! Working with larger structures:
+//!
+//! ```
+//! let large_array = array![1, 2, 3, 4, 5];
+//! let boxed_array = BoxTrait::new(large_array);
+//! ```
+//!
+//! Creating a recursive data structure:
+//!
+//!```
+//! #[derive(Copy, Drop, Debug)]
+//! enum BinaryTree {
+//!     Leaf: u32,
+//!     Node: (u32, Box<BinaryTree>, Box<BinaryTree>)
+//! }
+//!
+//! let leaf = BinaryTree::Leaf(1);
+//! let node = BinaryTree::Node((2, BoxTrait::new(leaf), BoxTrait::new(leaf)));
+//! println!("{:?}", node);
+//!```
+//!
+//! NOTE: A `Box<T>` is a smart pointer type that provides a way to store a value of type `T` in
+//! Cairo VM's _boxed_ segment, leaving only a pointer in the execution segment.
+
+/// A `Box` is a type that points to a wrapped value.
+/// It allows for cheap moving around of the value, as its size is small, and may wrap a large size.
 #[derive(Copy, Drop)]
 pub extern type Box<T>;
 
@@ -11,12 +49,15 @@ extern fn into_box<T>(value: T) -> Box<T> nopanic;
 extern fn unbox<T>(box: Box<T>) -> T nopanic;
 extern fn box_forward_snapshot<T>(value: @Box<T>) -> Box<@T> nopanic;
 
-/// Basic trait for the Box type.
+/// Basic trait for the `Box` type.
 #[generate_trait]
 pub impl BoxImpl<T> of BoxTrait<T> {
-    /// Creates a new Box with the given value.
+    /// Creates a new `Box` with the given value.
+    ///
+    /// Allocates space in the boxed segment for the provided value
+    /// and returns a `Box<T>` that points to it.
+    /// # Examples
     ///
-    /// Example:
     /// ```
     /// let x = 42;
     /// let boxed_x = BoxTrait::new(x);
@@ -26,22 +67,26 @@ pub impl BoxImpl<T> of BoxTrait<T> {
     fn new(value: T) -> Box<T> nopanic {
         into_box(value)
     }
-    /// Unboxes the given Box.
+
+    /// Unboxes the given `Box` and returns the wrapped value.
+    ///
+    /// # Examples
     ///
-    /// Example:
     /// ```
     /// let boxed = BoxTrait::new(42);
-    /// assert_eq!(boxed.unbox(), 42);
+    /// assert!(boxed.unbox() == 42);
     /// ```
     #[inline]
     #[must_use]
     fn unbox(self: Box<T>) -> T nopanic {
         unbox(self)
     }
-    /// Converts the given snapshot of a Box into a Box of a snapshot.
-    ///
+
+    /// Converts the given snapshot of a `Box` into a `Box` of a snapshot.
     /// Useful for structures that aren't copyable.
-    /// Example:
+    ///
+    /// # Examples
+    ///
     /// ```
     /// let snap_boxed_arr = @BoxTraits::new(array![1, 2, 3]);
     /// let boxed_snap_arr = snap_boxed_arr.as_snapshot();
@@ -54,13 +99,32 @@ pub impl BoxImpl<T> of BoxTrait<T> {
 }
 
 impl BoxDeref<T> of crate::ops::Deref<Box<T>> {
+    /// The target type after dereferencing.
     type Target = T;
+    /// Takes a `Box<T>`, deferences it and returns a value of type `T`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let boxed_value: Box<u32> = BoxTrait::new(1);
+    /// let value: u32 = boxed_value.deref();
+    /// assert!(value == 1);
+    /// ```
     fn deref(self: Box<T>) -> T {
         self.unbox()
     }
 }
 
 impl BoxDebug<T, impl TDebug: crate::fmt::Debug<T>> of crate::fmt::Debug<Box<T>> {
+    /// Formats a `Box` type, allowing to print `Box` instances for debugging purposes.
+    /// Boxed values are prefixed with `&` when formatted.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let boxed_value: Box<u32> = BoxTrait::new(1);
+    /// println!("{:?}", boxed_value); // Result will be `&1`
+    /// ```
     fn fmt(self: @Box<T>, ref f: crate::fmt::Formatter) -> Result<(), crate::fmt::Error> {
         write!(f, "&")?;
         TDebug::fmt(self.as_snapshot().unbox(), ref f)