part04.rs lines shortened

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

diff --git a/src/part14.rs b/src/part14.rs
index 6550fe52d2ed45c9e225bd76b79c9a9731585ac2..5c009059b527ea7b9659bd9c2af7d26b17da9230 100644 (file)
--- a/src/part14.rs
+++ b/src/part14.rs
@@ -15,8 +15,8 @@
 //@ `[T]` is the type of an (unsized) *array*, with elements of type `T`. All this means is that there's a contiguous
 //@ region of memory, where a bunch of `T` are stored. How many? We can't tell! This is an unsized type. Just like for
 //@ trait objects, this means we can only operate on pointers to that type, and these pointers will carry the missing
 //@ `[T]` is the type of an (unsized) *array*, with elements of type `T`. All this means is that there's a contiguous
 //@ region of memory, where a bunch of `T` are stored. How many? We can't tell! This is an unsized type. Just like for
 //@ trait objects, this means we can only operate on pointers to that type, and these pointers will carry the missing

-//@ information - namely, the length. Such a pointer is called a *slice*. As we will see, a slice can be split.
-//@ Our function can thus take a borrowed slice, and promise to sort all elements in there.
+//@ information - namely, the length (they will be *fat pointers*). Such a reference to an array is called a *slice*. As we will see, a slice can be split.
+//@ Our function can thus take a mutable slice, and promise to sort all elements in there.

 pub fn sort<T: PartialOrd>(data: &mut [T]) {
     if data.len() < 2 { return; }
 
 pub fn sort<T: PartialOrd>(data: &mut [T]) {
     if data.len() < 2 { return; }
 


@@ -27,7 +27,7 @@ pub fn sort<T: PartialOrd>(data: &mut [T]) {
     /* Invariant: pivot is data[0]; everything with index (0,lpos) is <= pivot;
        [rpos,len) is >= pivot; lpos < rpos */
     loop {
     /* 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. Write a
+        // **Exercise 14.1**: Complete this Quicksort loop. You can use `swap` on slices to swap two elements. Write a

         // test function for `sort`.
         unimplemented!()
     }
         // test function for `sort`.
         unimplemented!()
     }


@@ -38,7 +38,7 @@ pub fn sort<T: PartialOrd>(data: &mut [T]) {
     // Finally, we split our slice to sort the two halves. The nice part about slices is that splitting them is cheap:
     //@ They are just a pointer to a start address, and a length. We can thus get two pointers, one at the beginning and
     //@ one in the middle, and set the lengths appropriately such that they don't overlap. This is what `split_at_mut` does.
     // Finally, we split our slice to sort the two halves. The nice part about slices is that splitting them is cheap:
     //@ They are just a pointer to a start address, and a length. We can thus get two pointers, one at the beginning and
     //@ one in the middle, and set the lengths appropriately such that they don't overlap. This is what `split_at_mut` does.

-    //@ Since the two slices don't overlap, there is no aliasing and we can have them both mutably borrowed.
+    //@ Since the two slices don't overlap, there is no aliasing and we can have both of them as unique, mutable slices.

     let (part1, part2) = data.split_at_mut(lpos);
     //@ The index operation can not only be used to address certain elements, it can also be used for *slicing*: Giving a range
     //@ of indices, and obtaining an appropriate part of the slice we started with. Here, we remove the last element from
     let (part1, part2) = data.split_at_mut(lpos);
     //@ The index operation can not only be used to address certain elements, it can also be used for *slicing*: Giving a range
     //@ of indices, and obtaining an appropriate part of the slice we started with. Here, we remove the last element from


@@ -47,8 +47,8 @@ pub fn sort<T: PartialOrd>(data: &mut [T]) {
     sort(part2);                                                    /*@*/
 }
 
     sort(part2);                                                    /*@*/
 }
 

-// **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
+// **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!
 
 // Now, we can sort, e.g., an vector of numbers.
 // only, not by filename or line number!
 
 // Now, we can sort, e.g., an vector of numbers.


@@ -59,7 +59,7 @@ fn sort_nums(data: &mut Vec<i32>) {
 }
 
 // ## Arrays
 }
 
 // ## Arrays

-//@ An *array* in Rust is given be the type `[T; n]`, where `n` is some *fixed* number. So, `[f64; 10]` is an array of 10 floating-point
+//@ An *array* in Rust is given by the type `[T; n]`, where `n` is some *fixed* number. So, `[f64; 10]` is an array of 10 floating-point

 //@ numbers, all one right next to the other in memory. Arrays are sized, and hence can be used like any other type. But we can also
 //@ borrow them as slices, e.g., to sort them.
 fn sort_array() {
 //@ numbers, all one right next to the other in memory. Arrays are sized, and hence can be used like any other type. But we can also
 //@ borrow them as slices, e.g., to sort them.
 fn sort_array() {


@@ -69,7 +69,7 @@ fn sort_array() {
 
 // ## External Dependencies
 //@ This leaves us with just one more piece to complete rgrep: Taking arguments from the command-line. We could now directly work on
 
 // ## External Dependencies
 //@ This leaves us with just one more piece to complete rgrep: Taking arguments from the command-line. We could now directly work on

-//@ [`std::env::args`](http://doc.rust-lang.org/stable/std/env/fn.args.html) to gain access to those arguments, and this would become
+//@ [`std::env::args`](https://doc.rust-lang.org/stable/std/env/fn.args.html) to gain access to those arguments, and this would become

 //@ a pretty boring lesson in string manipulation. Instead, I want to use this opportunity to show how easy it is to benefit from
 //@ other people's work in your program.
 //@ 
 //@ a pretty boring lesson in string manipulation. Instead, I want to use this opportunity to show how easy it is to benefit from
 //@ other people's work in your program.
 //@ 


@@ -82,7 +82,7 @@ fn sort_array() {
 //@ arguments based on the usage string. External dependencies are declared in the `Cargo.toml` file.
 
 //@ I already prepared that file, but the declaration of the dependency is still commented out. So please open `Cargo.toml` of your workspace
 //@ arguments based on the usage string. External dependencies are declared in the `Cargo.toml` file.
 
 //@ I already prepared that file, but the declaration of the dependency is still commented out. So please open `Cargo.toml` of your workspace

-//@ now, and enabled the two commented-out lines. Then do `cargo build`. Cargo will now download the crate from crates.io, compile it,
+//@ now, and enable the two commented-out lines. Then do `cargo build`. Cargo will now download the crate from crates.io, compile it,

 //@ and link it to your program. In the future, you can do `cargo update` to make it download new versions of crates you depend on.
 //@ Note that crates.io is only the default location for dependencies, you can also give it the URL of a git repository or some local
 //@ path. All of this is explained in the [Cargo Guide](http://doc.crates.io/guide.html).
 //@ and link it to your program. In the future, you can do `cargo update` to make it download new versions of crates you depend on.
 //@ Note that crates.io is only the default location for dependencies, you can also give it the URL of a git repository or some local
 //@ path. All of this is explained in the [Cargo Guide](http://doc.crates.io/guide.html).


@@ -91,10 +91,11 @@ fn sort_array() {
 // Remove the attribute of the `rgrep` module to enable compilation.
 #[cfg(feature = "disabled")]
 pub mod rgrep {
 // 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 and then import shorter names with `use`. We also import some other pieces that we will need.
+    // 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;
     extern crate docopt;
     use self::docopt::Docopt;

-    use part12::{run, Options, OutputMode};
+    use part13::{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.
     use std::process;
 
     // The `USAGE` string documents how the program is to be called. It's written in a format that `docopt` can parse.


@@ -108,7 +109,7 @@ Options:
 
     // This function extracts the rgrep options from the command-line arguments.
     fn get_options() -> Options {
 
     // 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/).
+        // 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/>

         //@ The function `and_then` takes a closure from `T` to `Result<U, E>`, and uses it to transform a `Result<T, E>` to a
         //@ `Result<U, E>`. This way, we can chain computations that only happen if the previous one succeeded (and the error
         //@ type has to stay the same). In case you know about monads, this style of programming will be familiar to you.
         //@ The function `and_then` takes a closure from `T` to `Result<U, E>`, and uses it to transform a `Result<T, E>` to a
         //@ `Result<U, E>`. This way, we can chain computations that only happen if the previous one succeeded (and the error
         //@ type has to stay the same). In case you know about monads, this style of programming will be familiar to you.


@@ -130,8 +131,8 @@ Options:
         //@ encoded string, that is, a bunch of bytes in memory (`[u8]`) that are valid according of UTF-8. `str` is unsized. `&str`
         //@ stores the address of the character data, and their length. String literals like "this one" are
         //@ of type `&'static str`: They point right to the constant section of the binary, so 
         //@ encoded string, that is, a bunch of bytes in memory (`[u8]`) that are valid according of UTF-8. `str` is unsized. `&str`
         //@ stores the address of the character data, and their length. String literals like "this one" are
         //@ of type `&'static str`: They point right to the constant section of the binary, so 

-        //@ However, the borrow is valid for as long as the program runs, hence it has lifetime `'static`. Calling
-        //@ `to_string` will copy the string data into an owned buffer on the heap, and thus convert it to `String`.
+        //@ the reference is valid for the entire program. The bytes pointed to by `pattern`, on the other hand, are owned by someone else, 
+        //@ and we call `to_string` on it to copy the string data into a buffer on the heap that we own.

         let mode = if count {
             OutputMode::Count
         } else if sort {
         let mode = if count {
             OutputMode::Count
         } else if sort {


@@ -153,9 +154,9 @@ 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
+// **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.)
 
 // 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.)
 

-//@ [index](main.html) | [previous](part13.html) | [next](part15.html)
+//@ [index](main.html) | [previous](part13.html) | [raw source](workspace/src/part14.rs) | [next](part15.html)