A couple of fixes for the Box, stack and heap chapter.

src/std/box.md

@@ -1,9 +1,9 @@
 # Box, stack and heap
 
 All values in Rust are stack allocated by default. Values can be *boxed*
-(allocated in the heap) by creating a `Box<T>`. A box is a smart pointer to a
+(allocated on the heap) by creating a `Box<T>`. A box is a smart pointer to a
 heap allocated value of type `T`. When a box goes out of scope, its destructor
-is called, the inner object is destroyed, and the memory in the heap is freed.
+is called, the inner object is destroyed, and the memory on the heap is freed.
 
 Boxed values can be dereferenced using the `*` operator; this removes one layer
 of indirection. 
@@ -29,7 +29,7 @@ fn origin() -> Point {
 }
 
 fn boxed_origin() -> Box<Point> {
-    // Allocate this point in the heap, and return a pointer to it
+    // Allocate this point on the heap, and return a pointer to it
     Box::new(Point { x: 0.0, y: 0.0 })
 }
 
@@ -54,22 +54,22 @@ fn main() {
     // Double indirection
     let box_in_a_box: Box<Box<Point>> = Box::new(boxed_origin());
 
-    println!("Point occupies {} bytes in the stack",
+    println!("Point occupies {} bytes on the stack",
              mem::size_of_val(&point));
-    println!("Rectangle occupies {} bytes in the stack",
+    println!("Rectangle occupies {} bytes on the stack",
              mem::size_of_val(&rectangle));
 
-    // box size = pointer size
-    println!("Boxed point occupies {} bytes in the stack",
+    // box size == pointer size
+    println!("Boxed point occupies {} bytes on the stack",
              mem::size_of_val(&boxed_point));
-    println!("Boxed rectangle occupies {} bytes in the stack",
+    println!("Boxed rectangle occupies {} bytes on the stack",
              mem::size_of_val(&boxed_rectangle));
-    println!("Boxed box occupies {} bytes in the stack",
+    println!("Boxed box occupies {} bytes on the stack",
              mem::size_of_val(&box_in_a_box));
 
     // Copy the data contained in `boxed_point` into `unboxed_point`
     let unboxed_point: Point = *boxed_point;
-    println!("Unboxed point occupies {} bytes in the stack",
+    println!("Unboxed point occupies {} bytes on the stack",
              mem::size_of_val(&unboxed_point));
 }
 ```