fix solution for BigInt::min. Thanks, Derek!

[rust-101.git] / workspace / src / part14.rs

diff --git a/workspace/src/part14.rs b/workspace/src/part14.rs
index 37afcbc5b453cddb6a2428ad2b9aae20f2132c05..fb580f9c379d3e15fdd795b281f099454a9e00e9 100644 (file)
--- a/workspace/src/part14.rs
+++ b/workspace/src/part14.rs
@@ -1,69 +1,108 @@
-// Rust-101, Part 14: Mutex, Sync (WIP)
-// ==============================
+// Rust-101, Part 14: Slices, Arrays, External Dependencies
+// ========================================================

 
 

-use std::sync::{Arc, Mutex};
-use std::thread;

 
 

+// ## Slices

 
 

-// The derived `Clone` implementation will clone the `Arc`, so all clones will actually talk about the same counter.
-#[derive(Clone)]
-struct ConcurrentCounter(Arc<Mutex<usize>>);
+pub fn sort<T: PartialOrd>(data: &mut [T]) {
+    if data.len() < 2 { return; }

 
 

-impl ConcurrentCounter {
-    // The constructor should not be surprising.
-    pub fn new(val: usize) -> Self {
-        ConcurrentCounter(Arc::new(Mutex::new(val)))
+    // We decide that the element at 0 is our pivot, and then we move our cursors through the rest of the slice,
+    // making sure that everything on the left is no larger than the pivot, and everything on the right is no smaller.
+    let mut lpos = 1;
+    let mut rpos = data.len();
+    /* Invariant: pivot is data[0]; everything with index (0,lpos) is <= pivot;
+       [rpos,len) is >= pivot; lpos < rpos */
+    loop {
+        // **Exercise 14.1**: Complete this Quicksort loop. You can use `swap` on slices to swap two elements. Write a
+        // test function for `sort`.
+        unimplemented!()

     }
 
     }
 

-    pub fn increment(&self, by: usize) {
-        // `lock` on a mutex returns a *guard*, giving access to the data contained in the mutex.
-        let mut counter = self.0.lock().unwrap();
-        *counter = *counter + by;
-    }
+    // Once our cursors met, we need to put the pivot in the right place.
+    data.swap(0, lpos-1);

 
 

-    pub fn get(&self) -> usize {
-        let counter = self.0.lock().unwrap();
-        *counter
-    }
+    // Finally, we split our slice to sort the two halves. The nice part about slices is that splitting them is cheap:
+    let (part1, part2) = data.split_at_mut(lpos);
+    unimplemented!()

 }
 
 }
 

-// Now our counter is ready for action.
-pub fn main() {
-    let counter = ConcurrentCounter::new(0);
+// **Exercise 14.2**: Since `String` implements `PartialEq`, you can now change the function `output_lines` in the previous part
+// to call the sort function above. If you did exercise 13.1, you will have slightly more work. Make sure you sort by the matched line
+// only, not by filename or line number!

 
 

-    // We clone the counter for the first thread, which increments it by 2 every 15ms.
-    let counter1 = counter.clone();
-    let handle1 = thread::spawn(move || {
-        for _ in 0..10 {
-            thread::sleep_ms(15);
-            counter1.increment(2);
-        }
-    });
-
-    // The second thread increments the counter by 3 every 20ms.
-    let counter2 = counter.clone();
-    let handle2 = thread::spawn(move || {
-        for _ in 0..10 {
-            thread::sleep_ms(20);
-            counter2.increment(3);
+// Now, we can sort, e.g., an vector of numbers.
+fn sort_nums(data: &mut Vec<i32>) {
+    sort(&mut data[..]);
+}
+
+// ## Arrays
+fn sort_array() {
+    let mut array_of_data: [f64; 5] = [1.0, 3.4, 12.7, -9.12, 0.1];
+    sort(&mut array_of_data);
+}
+
+// ## External Dependencies
+
+
+// I disabled the following module (using a rather bad hack), because it only compiles if `docopt` is linked.
+// Remove the attribute of the `rgrep` module to enable compilation.
+#[cfg(feature = "disabled")]
+pub mod rgrep {
+    // Now that `docopt` is linked, we can first add it to the namespace with `extern crate` and then import shorter names with `use`.
+    // We also import some other pieces that we will need.
+    extern crate docopt;
+    use self::docopt::Docopt;
+    use part12::{run, Options, OutputMode};
+    use std::process;
+
+    // The `USAGE` string documents how the program is to be called. It's written in a format that `docopt` can parse.
+    static USAGE: &'static str = "
+Usage: rgrep [-c] [-s] <pattern> <file>...
+
+Options:
+    -c, --count  Count number of matching lines (rather than printing them).
+    -s, --sort   Sort the lines before printing.
+";
+
+    // This function extracts the rgrep options from the command-line arguments.
+    fn get_options() -> Options {
+        // This parses `argv` and exit the program with an error message if it fails. The code is taken from the [`docopt` documentation](http://burntsushi.net/rustdoc/docopt/). <br/>
+        let args = Docopt::new(USAGE).and_then(|d| d.parse()).unwrap_or_else(|e| e.exit());
+        // Now we can get all the values out.
+        let count = args.get_bool("-c");
+        let sort = args.get_bool("-s");
+        let pattern = args.get_str("<pattern>");
+        let files = args.get_vec("<file>");
+        if count && sort {
+            println!("Setting both '-c' and '-s' at the same time does not make any sense.");
+            process::exit(1);

         }
         }

-    });

 
 

-    // Now we want to watch the threads working on the counter.
-    for _ in 0..50 {
-        thread::sleep_ms(5);
-        println!("Current value: {}", counter.get());
+        // We need to make the strings owned to construct the `Options` instance.
+        let mode = if count {
+            OutputMode::Count
+        } else if sort {
+            OutputMode::SortAndPrint
+        } else {
+            OutputMode::Print
+        };
+        Options {
+            files: files.iter().map(|file| file.to_string()).collect(),
+            pattern: pattern.to_string(),
+            output_mode: mode,
+        }

     }
 
     }
 

-    // Finally, wait for all the threads to finish to be sure we can catch the counter's final value.
-    handle1.join().unwrap();
-    handle2.join().unwrap();
-    println!("Final value: {}", counter.get());
+    // Finally, we can call the `run` function from the previous part on the options extracted using `get_options`. Edit `main.rs` to call this function.
+    // You can now use `cargo run -- <pattern> <files>` to call your program, and see the argument parser and the threads we wrote previously in action!
+    pub fn main() {
+        unimplemented!()
+    }

 }
 
 }
 

-// **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 14.3**: Wouldn't it be nice if rgrep supported regular expressions? There's already a crate that does all the parsing and matching on regular
+// expression, it's called [regex](https://crates.io/crates/regex). Add this crate to the dependencies of your workspace, add an option ("-r") to switch
+// the pattern to regular-expression mode, and change `filter_lines` to honor this option. The documentation of regex is available from its crates.io site.
+// (You won't be able to use the `regex!` macro if you are on the stable or beta channel of Rust. But it wouldn't help for our use-case anyway.)