added nullptr example

Author: BartMassey

README.md

@@ -48,3 +48,4 @@ in a controlled repository now.
 * `debug-macro-rep.rs`: example of macro with varargs
 * `macro-nargs.rs`: example of recursive macro
 * `macro-tt.rs`: macro token tree example
+* `nullptr.rs`: null pointer example

nullptr.rs

@@ -0,0 +1,10 @@
+fn main() {
+    let mut p: * const u32 = std::ptr::null::<u32>();
+    println!("{:?}", p);
+    println!("{:?}", p.is_null());
+    p = p.wrapping_add(1);
+    println!("{:?}", p);
+
+    let p: *const u8 = "🦀ello".as_ptr();
+    println!("{}", unsafe { (*p) as char });
+}