Merge pull request #1651 from adrian5/cleanup

Clean up Chapter 2 (Primitives)

Author: marioidival

src/primitives.md

@@ -2,28 +2,27 @@
 
 Rust provides access to a wide variety of `primitives`. A sample includes:
 
-
 ### Scalar Types
 
-* signed integers: `i8`, `i16`, `i32`, `i64`, `i128` and `isize` (pointer size)
-* unsigned integers: `u8`, `u16`, `u32`, `u64`, `u128` and `usize` (pointer
+* Signed integers: `i8`, `i16`, `i32`, `i64`, `i128` and `isize` (pointer size)
+* Unsigned integers: `u8`, `u16`, `u32`, `u64`, `u128` and `usize` (pointer
   size)
-* floating point: `f32`, `f64`
+* Floating point: `f32`, `f64`
 * `char` Unicode scalar values like `'a'`, `'α'` and `'∞'` (4 bytes each)
 * `bool` either `true` or `false`
-* and the unit type `()`, whose only possible value is an empty tuple: `()`
+* The unit type `()`, whose only possible value is an empty tuple: `()`
 
-Despite the value of a unit type being a tuple, it is not considered a
-compound type because it does not contain multiple values. 
+Despite the value of a unit type being a tuple, it is not considered a compound
+type because it does not contain multiple values.
 
 ### Compound Types
 
-* arrays like `[1, 2, 3]`
-* tuples like `(1, true)`
+* Arrays like `[1, 2, 3]`
+* Tuples like `(1, true)`
 
-Variables can always be *type annotated*. Numbers may additionally be
-annotated via a *suffix* or *by default*. Integers default to `i32` and
-floats to `f64`. Note that Rust can also infer types from context.
+Variables can always be *type annotated*. Numbers may additionally be annotated
+via a *suffix* or *by default*. Integers default to `i32` and floats to `f64`.
+Note that Rust can also infer types from context.
 
 ```rust,editable,ignore,mdbook-runnable
 fn main() {
@@ -36,26 +35,27 @@ fn main() {
     // Or a default will be used.
     let default_float   = 3.0; // `f64`
     let default_integer = 7;   // `i32`
-    
-    // A type can also be inferred from context 
-    let mut inferred_type = 12; // Type i64 is inferred from another line
+
+    // A type can also be inferred from context.
+    let mut inferred_type = 12; // Type i64 is inferred from another line.
     inferred_type = 4294967296i64;
-    
+
     // A mutable variable's value can be changed.
     let mut mutable = 12; // Mutable `i32`
     mutable = 21;
-    
+
     // Error! The type of a variable can't be changed.
     mutable = true;
-    
+
     // Variables can be overwritten with shadowing.
     let mutable = true;
 }
 ```
 
 ### See also:
 
-[the `std` library][std], [`mut`][mut], [`inference`][inference], and [`shadowing`][shadowing]
+[the `std` library][std], [`mut`][mut], [`inference`][inference], and
+[`shadowing`][shadowing]
 
 [std]: https://doc.rust-lang.org/std/
 [mut]: variable_bindings/mut.md

src/primitives/array.md

@@ -5,66 +5,65 @@ memory. Arrays are created using brackets `[]`, and their length, which is known
 at compile time, is part of their type signature `[T; length]`.
 
 Slices are similar to arrays, but their length is not known at compile time.
-Instead, a slice is a two-word object, the first word is a pointer to the data,
-and the second word is the length of the slice. The word size is the same as
-usize, determined by the processor architecture e.g. 64 bits on an x86-64.
-Slices can be used to borrow a section of an array, and have the type signature
-`&[T]`.
+Instead, a slice is a two-word object; the first word is a pointer to the data,
+the second word the length of the slice. The word size is the same as usize,
+determined by the processor architecture, e.g. 64 bits on an x86-64. Slices can
+be used to borrow a section of an array and have the type signature `&[T]`.
 
 ```rust,editable,ignore,mdbook-runnable
 use std::mem;
 
-// This function borrows a slice
+// This function borrows a slice.
 fn analyze_slice(slice: &[i32]) {
-    println!("first element of the slice: {}", slice[0]);
-    println!("the slice has {} elements", slice.len());
+    println!("First element of the slice: {}", slice[0]);
+    println!("The slice has {} elements", slice.len());
 }
 
 fn main() {
-    // Fixed-size array (type signature is superfluous)
+    // Fixed-size array (type signature is superfluous).
     let xs: [i32; 5] = [1, 2, 3, 4, 5];
 
-    // All elements can be initialized to the same value
+    // All elements can be initialized to the same value.
     let ys: [i32; 500] = [0; 500];
 
-    // Indexing starts at 0
-    println!("first element of the array: {}", xs[0]);
-    println!("second element of the array: {}", xs[1]);
+    // Indexing starts at 0.
+    println!("First element of the array: {}", xs[0]);
+    println!("Second element of the array: {}", xs[1]);
 
-    // `len` returns the count of elements in the array
-    println!("number of elements in array: {}", xs.len());
+    // `len` returns the count of elements in the array.
+    println!("Number of elements in array: {}", xs.len());
 
-    // Arrays are stack allocated
-    println!("array occupies {} bytes", mem::size_of_val(&xs));
+    // Arrays are stack allocated.
+    println!("Array occupies {} bytes", mem::size_of_val(&xs));
 
-    // Arrays can be automatically borrowed as slices
-    println!("borrow the whole array as a slice");
+    // Arrays can be automatically borrowed as slices.
+    println!("Borrow the whole array as a slice.");
     analyze_slice(&xs);
 
-    // Slices can point to a section of an array
-    // They are of the form [starting_index..ending_index]
-    // starting_index is the first position in the slice
-    // ending_index is one more than the last position in the slice
-    println!("borrow a section of the array as a slice");
+    // Slices can point to a section of an array.
+    // They are of the form [starting_index..ending_index].
+    // `starting_index` is the first position in the slice.
+    // `ending_index` is one more than the last position in the slice.
+    println!("Borrow a section of the array as a slice.");
     analyze_slice(&ys[1 .. 4]);
 
-    // Example of empty slice `&[]`
+    // Example of empty slice `&[]`:
     let empty_array: [u32; 0] = [];
     assert_eq!(&empty_array, &[]);
-    assert_eq!(&empty_array, &[][..]); // same but more verbose
+    assert_eq!(&empty_array, &[][..]); // Same but more verbose
 
     // Arrays can be safely accessed using `.get`, which returns an
     // `Option`. This can be matched as shown below, or used with
     // `.expect()` if you would like the program to exit with a nice
     // message instead of happily continue.
-    for i in 0..xs.len() + 1 { // OOPS, one element too far
+    for i in 0..xs.len() + 1 { // Oops, one element too far!
         match xs.get(i) {
             Some(xval) => println!("{}: {}", i, xval),
             None => println!("Slow down! {} is too far!", i),
         }
     }
 
-    // Out of bound indexing causes runtime error
+    // Out of bound indexing causes runtime error.
     //println!("{}", xs[5]);
 }
 ```

src/primitives/literals.md

@@ -9,12 +9,15 @@ notation using these prefixes respectively: `0x`, `0o` or `0b`.
 Underscores can be inserted in numeric literals to improve readability, e.g.
 `1_000` is the same as `1000`, and `0.000_001` is the same as `0.000001`.
 
+Rust also supports scientific [E-notation][enote], e.g. `1e6`, `7.6e-4`. The
+associated type is `f64`.
+
 We need to tell the compiler the type of the literals we use. For now,
 we'll use the `u32` suffix to indicate that the literal is an unsigned 32-bit
 integer, and the `i32` suffix to indicate that it's a signed 32-bit integer.
 
-The operators available and their precedence [in Rust][rust op-prec] are similar to other
-[C-like languages][op-prec].
+The operators available and their precedence [in Rust][rust op-prec] are similar
+to other [C-like languages][op-prec].
 
 ```rust,editable
 fn main() {
@@ -25,6 +28,9 @@ fn main() {
     println!("1 - 2 = {}", 1i32 - 2);
     // TODO ^ Try changing `1i32` to `1u32` to see why the type is important
 
+    // Scientific notation
+    println!("1e4 is {}, -2.5e-3 is {}", 1e4, -2.5e-3);
+
     // Short-circuiting boolean logic
     println!("true AND false is {}", true && false);
     println!("true OR false is {}", true || false);
@@ -42,5 +48,6 @@ fn main() {
 }
 ```
 
+[enote]: https://en.wikipedia.org/wiki/Scientific_notation#E_notation
 [rust op-prec]: https://doc.rust-lang.org/reference/expressions.html#expression-precedence
 [op-prec]: https://en.wikipedia.org/wiki/Operator_precedence#Programming_languages

src/primitives/tuples.md

@@ -6,9 +6,9 @@ using parentheses `()`, and each tuple itself is a value with type signature
 use tuples to return multiple values, as tuples can hold any number of values.
 
 ```rust,editable
-// Tuples can be used as function arguments and as return values
+// Tuples can be used as function arguments and as return values.
 fn reverse(pair: (i32, bool)) -> (bool, i32) {
-    // `let` can be used to bind the members of a tuple to variables
+    // `let` can be used to bind the members of a tuple to variables.
     let (int_param, bool_param) = pair;
 
     (bool_param, int_param)
@@ -19,79 +19,78 @@ fn reverse(pair: (i32, bool)) -> (bool, i32) {
 struct Matrix(f32, f32, f32, f32);
 
 fn main() {
-    // A tuple with a bunch of different types
+    // A tuple with a bunch of different types.
     let long_tuple = (1u8, 2u16, 3u32, 4u64,
                       -1i8, -2i16, -3i32, -4i64,
                       0.1f32, 0.2f64,
                       'a', true);
 
-    // Values can be extracted from the tuple using tuple indexing
-    println!("long tuple first value: {}", long_tuple.0);
-    println!("long tuple second value: {}", long_tuple.1);
+    // Values can be extracted from the tuple using tuple indexing.
+    println!("Long tuple first value: {}", long_tuple.0);
+    println!("Long tuple second value: {}", long_tuple.1);
 
-    // Tuples can be tuple members
+    // Tuples can be tuple members.
     let tuple_of_tuples = ((1u8, 2u16, 2u32), (4u64, -1i8), -2i16);
 
-    // Tuples are printable
+    // Tuples are printable.
     println!("tuple of tuples: {:?}", tuple_of_tuples);
-    
-    // But long Tuples (more than 12 elements) cannot be printed
-    // let too_long_tuple = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13);
-    // println!("too long tuple: {:?}", too_long_tuple);
+
+    // But long Tuples (more than 12 elements) cannot be printed.
+    //let too_long_tuple = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13);
+    //println!("Too long tuple: {:?}", too_long_tuple);
     // TODO ^ Uncomment the above 2 lines to see the compiler error
 
     let pair = (1, true);
-    println!("pair is {:?}", pair);
+    println!("Pair is {:?}", pair);
 
-    println!("the reversed pair is {:?}", reverse(pair));
+    println!("Uhe reversed pair is {:?}", reverse(pair));
 
     // To create one element tuples, the comma is required to tell them apart
-    // from a literal surrounded by parentheses
-    println!("one element tuple: {:?}", (5u32,));
-    println!("just an integer: {:?}", (5u32));
+    // from a literal surrounded by parentheses.
+    println!("One element tuple: {:?}", (5u32,));
+    println!("Just an integer: {:?}", (5u32));
 
-    //tuples can be destructured to create bindings
+    // Tuples can be destructured to create bindings.
     let tuple = (1, "hello", 4.5, true);
 
     let (a, b, c, d) = tuple;
     println!("{:?}, {:?}, {:?}, {:?}", a, b, c, d);
 
     let matrix = Matrix(1.1, 1.2, 2.1, 2.2);
     println!("{:?}", matrix);
-
 }
 ```
 
 ### Activity
 
- 1. *Recap*: Add the `fmt::Display` trait to the `Matrix` struct in the above example,
-    so that if you switch from printing the debug format `{:?}` to the display
-    format `{}`, you see the following output:
-
-    ```text
-    ( 1.1 1.2 )
-    ( 2.1 2.2 )
-    ```
-
-    You may want to refer back to the example for [print display][print_display].
- 2. Add a `transpose` function using the `reverse` function as a template, which
-    accepts a matrix as an argument, and returns a matrix in which two elements
-    have been swapped. For example:
-
-    ```rust,ignore
-    println!("Matrix:\n{}", matrix);
-    println!("Transpose:\n{}", transpose(matrix));
-    ```
-
-    results in the output:
-
-    ```text
-    Matrix:
-    ( 1.1 1.2 )
-    ( 2.1 2.2 )
-    Transpose:
-    ( 1.1 2.1 )
-    ( 1.2 2.2 )
-    ```
+1. *Recap*: Add the `fmt::Display` trait to the `Matrix` struct in the above
+   example, so that if you switch from printing the debug format `{:?}` to the
+   display format `{}`, you see the following output:
+
+   ```text
+   ( 1.1 1.2 )
+   ( 2.1 2.2 )
+   ```
+
+   You may want to refer back to the example for [print display][print_display].
+2. Add a `transpose` function using the `reverse` function as a template, which
+   accepts a matrix as an argument, and returns a matrix in which two elements
+   have been swapped. For example:
+
+   ```rust,ignore
+   println!("Matrix:\n{}", matrix);
+   println!("Transpose:\n{}", transpose(matrix));
+   ```
+
+   Results in the output:
+
+   ```text
+   Matrix:
+   ( 1.1 1.2 )
+   ( 2.1 2.2 )
+   Transpose:
+   ( 1.1 2.1 )
+   ( 1.2 2.2 )
+   ```
 
 [print_display]: ../hello/print/print_display.md