re-do deepaksirone's fix on the actual source file

[rust-101.git] / workspace / src / part15.rs

diff --git a/workspace/src/part15.rs b/workspace/src/part15.rs
index d006b23ae92f220c3c27ba5fc122139a0b64e04d..148f64845c74afc7db39f8450955aab0c39ae2f1 100644 (file)
--- a/workspace/src/part15.rs
+++ b/workspace/src/part15.rs
@@ -1,8 +1,9 @@
-// Rust-101, Part 15: Mutex, Interior Mutability (cont.), Sync
-// ===========================================================
+// Rust-101, Part 15: Mutex, Interior Mutability (cont.), RwLock, Sync
+// ===================================================================
 
 use std::sync::{Arc, Mutex};
 use std::thread;
+use std::time::Duration;
 
 
 // The derived `Clone` implementation will clone the `Arc`, so all clones will actually talk about the same counter.
@@ -15,8 +16,9 @@ impl ConcurrentCounter {
         unimplemented!()
     }
 
+    // The core operation is, of course, `increment`.
     pub fn increment(&self, by: usize) {
-        // `lock` on a mutex returns a *guard*, giving access to the data contained in the mutex.
+        // `lock` on a mutex returns a guard, very much like `RefCell`. The guard gives access to the data contained in the mutex.
         let mut counter = self.0.lock().unwrap();
         *counter = *counter + by;
     }
@@ -35,7 +37,7 @@ pub fn main() {
     let counter1 = counter.clone();
     let handle1 = thread::spawn(move || {
         for _ in 0..10 {
-            thread::sleep_ms(15);
+            thread::sleep(Duration::from_millis(15));
             counter1.increment(2);
         }
     });
@@ -44,14 +46,14 @@ pub fn main() {
     let counter2 = counter.clone();
     let handle2 = thread::spawn(move || {
         for _ in 0..10 {
-            thread::sleep_ms(20);
+            thread::sleep(Duration::from_millis(20));
             counter2.increment(3);
         }
     });
 
     // Now we watch the threads working on the counter.
     for _ in 0..50 {
-        thread::sleep_ms(5);
+        thread::sleep(Duration::from_millis(5));
         println!("Current value: {}", counter.get());
     }
 
@@ -61,16 +63,13 @@ pub fn main() {
     println!("Final value: {}", counter.get());
 }
 
-// **Exercise 14.1**: Besides `Mutex`, there's also [`RwLock`](http://doc.rust-lang.org/stable/std/sync/struct.RwLock.html), which
-// provides two ways of locking: One that grants only read-only access, to any number of concurrent readers, and another one
-// for exclusive write access. (Notice that this is the same pattern we already saw with shared vs. mutable borrows.) Change
-// the code above to use `RwLock`, such that multiple calls to `get` can be executed at the same time.
-// 
-// **Exercise 14.2**: Add an operation `compare_and_inc(&self, test: usize, by: usize)` that increments the counter by
+// **Exercise 15.1**: Add an operation `compare_and_inc(&self, test: usize, by: usize)` that increments the counter by
 // `by` *only if* the current value is `test`.
+// 
+// **Exercise 15.2**: Rather than panicking in case the lock is poisoned, we can use `into_inner` on the error to recover
+// the data inside the lock. Change the code above to do that. Try using `unwrap_or_else` for this job.
 
 
-// FIXME TODO some old outdated explanation FIXME TODO
-
+// **Exercise 15.3**:  Change the code above to use `RwLock`, such that multiple calls to `get` can be executed at the same time.