From: Ralf Jung <post@ralfj.de>
Date: Mon, 22 Jun 2015 11:39:08 +0000 (+0200)
Subject: Java actually doesn't do pointer checks all the time
X-Git-Url: https://git.ralfj.de/rust-101.git/commitdiff_plain/1b77423cf168e5ff2b41667ea67252f4fbc44652?ds=sidebyside

Java actually doesn't do pointer checks all the time
---

diff --git a/src/part04.rs b/src/part04.rs
index e4c6a59..14deb89 100644
--- a/src/part04.rs
+++ b/src/part04.rs
@@ -86,10 +86,10 @@ fn shared_borrow_demo() {
     vec_min(&v);
     println!("The first element is: {}", *first);
 }
-// What's going on here? First, `&` is how you create a shared borrow to something. This code creates three
-// shared borrows to `v`: The borrow for `first` begins in the 2nd line of the function and lasts all the way to
-// the end. The other two borrows, created for calling `vec_min`, only last for the duration of that
-// respective call.
+// What's going on here? First, `&` is how you create a shared borrow to something. All borrows are created like
+// this - there is no way to have something like a  NULL pointer. This code creates three shared borrows to `v`:
+// The borrow for `first` begins in the 2nd line of the function and lasts all the way to the end. The other two
+// borrows, created for calling `vec_min`, only last for the duration of that respective call.
 // 
 // Technically, of course, borrows are pointers. Notice that since `vec_min` only gets a shared
 // borrow, Rust knows that it cannot mutate `v` in any way. Hence the pointer into the buffer of `v`
diff --git a/src/part07.rs b/src/part07.rs
index a996a22..65d6823 100644
--- a/src/part07.rs
+++ b/src/part07.rs
@@ -27,9 +27,7 @@ pub fn vec_min<T: Minimum>(v: &Vec<T>) -> Option<&T> {
 // Notice that the return type `Option<&T>` is technically (leaving the borrowing story aside) a
 // pointer to a `T`, that could optionally be invalid. In other words, it's just like a pointer in
 // C(++) or Java that can be `NULL`! However, thanks to `Option` being an `enum`, we cannot forget
-// to check the pointer for validity, avoiding the safety issues of C(++). At the same time, when we
-// have a borrow like `v` above that's not an `Option`, we *know* that is has to be a valid
-// pointer, so we don't even need to do the `NULL`-check that Java does all the time.<br/>
+// to check the pointer for validity, avoiding the safety issues of C(++).<br/>
 // Also, if you are worried about wasting space, notice that Rust knows that `&T` can never be
 // `NULL`, and hence optimizes `Option<&T>` to be no larger than `&T`. The `None` case is represented
 // as `NULL`. This is another great example of a zero-cost abstraction: `Option<&T>` is exactly like