X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/5f6e02d64e3789115ea4327a045b8ad3c39b1808..bae9e47884fdc3fc1a81fb4844572a832fcfb2ce:/workspace/src/part13.rs?ds=sidebyside

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+// Rust-101, Part 13: Slices, Arrays, External Dependencies
+// =================
+
+
+// ## Slices
+pub fn sort<T: PartialOrd>(data: &mut [T]) {
+    if data.len() < 2 { return; }
+
+    // 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 13.1**: Complete this Quicksort loop. You can use `swap` on slices to swap two elements.
+        unimplemented!()
+    }
+
+    // Once our cursors met, we need to put the pivot in the right place.
+    data.swap(0, lpos-1);
+
+    // 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!()
+}
+
+// **Exercise 13.2*: 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 12.1, you will have slightly more work. Make sure you sort by the matched line
+// only, not by filename or line number!
+
+// 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 data: [f64; 5] = [1.0, 3.4, 12.7, -9.12, 0.1];
+    sort(&mut data);
+}
+
+// ## External Dependencies
+
+
+// I disabled the following module (using a rather bad hack), because it only compiles if `docopt` is linked. However, before enabling it,
+// you still have get the external library into the global namespace. This is done with `extern crate docopt;`, and that statement *has* to be
+// in `main.rs`. So please go there, and enable this commented-out line. Then remove the attribute of the following module.
+#[cfg(feature = "disabled")]
+pub mod rgrep {
+    // Now that `docopt` is linked and declared in `main.rs`, we can import it with `use`. We also import some other pieces that we will need.
+    use 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 {
+        // Parse argv and exit the program with an error message if it fails. This is taken from the [`docopt` documentation](http://burntsushi.net/rustdoc/docopt/).
+        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);
+        }
+
+        // We need to make the strings owned to construct the `Options` instance.
+        Options {
+            files: files.iter().map(|file| file.to_string()).collect(),
+            pattern: pattern.to_string(),
+            output_mode: if count { OutputMode::Count } else if sort { OutputMode::SortAndPrint } else { OutputMode::Print },
+        }
+    }
+
+    // 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() {
+        run(get_options());
+    }
+}
+
+// **Exercise 13.3**: 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.
+