exercises + threads

Cargo.toml

@@ -2,5 +2,11 @@
 name = "rust-by-example"
 version = "0.1.0"
 edition = "2021"
+default-run = "rust-by-example"
 
 [dependencies]
+rand = "0.9.2"
+reqwest = "0.12.22"
+# clap = "2.27.1" # from crates.io
+# rand = { git = "https://github.com/rust-lang-nursery/rand" } # from online repo
+# bar = { path = "../bar" } # from a path in the local filesystem

README.md

@@ -1 +1 @@
-# Rust by example
+# [Rust by example](https://doc.rust-lang.org/stable/rust-by-example/)

src/bin/secondary_main.rs

@@ -0,0 +1,4 @@
+fn main() {
+    println!("This was ran with '$ cargo run --bin secondary_main'");
+    println!("This is a secondary main!");
+}

src/concepts/box_basics.rs

@@ -0,0 +1,14 @@
+fn box_integer(number: i32) -> Box<i32> {
+    Box::new(number)
+}
+
+fn box_function() -> Box<fn(i32) -> Box<i32>> {
+    Box::new(box_integer)
+}
+
+pub fn box_basics() {
+    let boxed_int = box_integer(3);
+    let boxed_boxer = box_function();
+    let another_boxed_int = boxed_boxer(4);
+    print!("Box basics: {} {}", boxed_int, another_boxed_int);
+}

src/concepts/mod.rs

@@ -0,0 +1,3 @@
+mod box_basics;
+
+pub use box_basics::box_basics;

src/controlflow.rs

@@ -195,4 +195,45 @@ pub fn control_flow_module() {
         n @ 1..5 => println!("{n} is between 1 and 5"),
         _ => (),
     }
+
+    // If let
+    // Lets you simplify destructuring
+    // Usefull if objecto neither implements nor derives PartialEq (cant do variable == Object::A)
+    if let n @ 1..5 = another_number {
+        println!("{n} is between 1 and 5");
+    }
+
+    // can also be used to match an enum
+    enum Fooo {
+        A,
+        B,
+        Another(u32),
+    };
+
+    let a = Fooo::A;
+    let b = Fooo::Another(3);
+
+    if let Fooo::A = a {
+        println!("a is A");
+    }
+
+    if let Fooo::Another(n) = b {
+        println!("b is another({n})");
+    }
+
+    // Let else
+    //<span class="underline"> Acts as a try - catch when delcaring variables
+
+    // while let
+    // Similar to if let, to make match sequences more tolerable
+    let mut optional = Some(0);
+
+    while let Some(i) = optional {
+        if i > 9 {
+            println!("Greater than 9");
+            optional = None;
+        } else {
+            optional = Some(i + 1);
+        }
+    }
 }

src/exercises/easy_difficulty.rs

@@ -0,0 +1,65 @@
+pub fn binary_search<T>(list: &[T], value: T) -> Result<usize, &'static str>
+where
+    T: PartialOrd + Clone,
+{
+    if !is_sorted(list) {
+        return Err("Input list must be sorted");
+    }
+
+    let mut current_slice = list;
+    let mut original_index: Option<usize> = None;
+    while !current_slice.is_empty() {
+        let middle = current_slice.len() / 2;
+
+        if current_slice[middle] == value {
+            let result = match original_index {
+                Some(i) => i + middle,
+                None => middle,
+            };
+            return Ok(result);
+        }
+        if middle < 1 {
+            return Err("Not found");
+        }
+        if current_slice[middle] > value {
+            current_slice = current_slice.split_at(middle).0;
+        } else {
+            current_slice = current_slice.split_at(middle).1;
+            if original_index.is_none() {
+                original_index = Some(middle);
+            } else {
+                original_index = Some(original_index.unwrap() + middle);
+            }
+        }
+    }
+    Err("Not found")
+}
+
+pub fn is_sorted<T>(list: &[T]) -> bool
+where
+    T: PartialOrd,
+{
+    for index in 1..list.len() {
+        if list[index] < list[index - 1] {
+            return false;
+        }
+    }
+    true
+}
+
+// TODO: read about good practices when using mutable parameters
+// maybe the correct thing to do is to take an immutable one and create a copy inside the function.
+pub fn bubble_sort<T>(mut list: Vec<T>) -> Vec<T>
+where
+    T: PartialOrd,
+{
+    for lap in 1..list.len() {
+        for index in (lap..list.len()).rev() {
+            if list[index] < list[index - 1] {
+                list.swap(index, index - 1);
+            }
+        }
+    }
+
+    list
+}

src/exercises/hard_difficulty.rs

@@ -0,0 +1,66 @@
+/*
+*
+Exercise: Implement a Multithreaded Web Crawler
+
+#### Objective:
+Create a simple multithreaded web crawler in Rust that can visit a set of web pages concurrently and extract all the links from those pages.
+
+#### Requirements:
+1. **Concurrent Fetching:** The crawler should utilize multiple threads to fetch web pages to improve performance.
+2. **Link Extraction:** For each page visited by the crawler, extract all the hyperlinks (`<a href="...">`) present on the page.
+3. **Avoid Cycles:** Ensure the crawler doesn't visit the same page more than once.
+4. **Limit Depth:** Allow the user to specify the maximum depth for crawling (i.e., the maximum number of links to follow from the initial set of given URLs).
+5. **Graceful Shutdown:** Allow the crawler to be stopped gracefully upon receiving a user interrupt (like pressing Ctrl+C).
+
+#### Steps to Implement:
+1. **Set Up the Project:**
+   - Create a new Rust project using Cargo.
+
+2. **Implement URL Fetching:**
+   - Use `reqwest` or a similar library to fetch the contents of a web page.
+   - Handle networking errors gracefully.
+
+3. **Extract Links:**
+   - Use the `scraper` crate or implement your own HTML parsing logic to extract links from the fetched HTML content.
+
+4. **Multithreading:**
+   - Utilize Rust's `std::thread` or the `tokio` runtime to spawn threads that can concurrently fetch and process web pages.
+
+5. **Avoid Revisits:**
+   - Maintain a `HashSet` or similar structure to keep track of visited URLs to prevent revisiting the same page.
+
+6. **Depth Control:**
+   - Use a data structure (like a queue) to manage the list of URLs to visit, and keep track of the current depth level for each URL.
+
+7. **Graceful Shutdown:**
+   - Implement signal handling to catch user interrupts and terminate the crawling process gracefully.
+
+8. **Testing:**
+   - Write tests to ensure the crawler functions as expected, including edge cases like broken links, non-responsive pages, etc.
+
+#### Hints:
+- Consider using Rust's ownership model to manage shared state across threads safely.
+- Make use of concurrency primitives like `Arc` and `Mutex` to safely share data between threads.
+- Efficiently manage the queue of URLs to visit, making sure to handle potential deadlocks and race conditions.
+
+This exercise will test the candidate's ability to work with network requests, concurrency, and data structures in Rust, while also evaluating their understanding of graceful error handling and software design.
+*/
+
+// #[derive(Debug)]
+// struct HyperLink<'a> {
+//     href: &'a str,
+//     label: &'a str,
+// }
+
+// struct PageData<'a> {
+//     links: Vec<HyperLink<'a>>,
+//     url: &'a str,
+// }
+
+// pub fn web_crawler(url_list: Vec<&str>) -> Vec<PageData> {}
+
+// fn get_page_links(url: &str) -> PageData {
+//     PageData { links: (), url }
+// }
+
+// fn get_page_body(url: &str) -> &str {}

src/exercises/medium.rs

@@ -1,23 +0,0 @@
-pub fn longest_palindrome(value: &str) -> String {
-    let mut lp: String = "0".to_string();
-    let input_size = value.len() - 1;
-
-    for pal_size in 2..=input_size {
-        for i in 0..input_size {
-            if input_size - i < pal_size {
-                break;
-            }
-            if let Some(slice) = value.get(i..(i + pal_size - 1)) {
-                // let reverted_slice = slice.chars().rev().collect::<String>();
-                // if string was mutable, we count use .reserve()
-                let reverted_slice = slice.chars().rev().collect::<String>();
-                if slice == reverted_slice {
-                    lp = reverted_slice;
-                    break;
-                }
-            }
-        }
-    }
-
-    lp
-}

src/exercises/medium_difficulty.rs

@@ -0,0 +1,101 @@
+/*
+ * Count squares
+ */
+pub fn count_squares(matrix: &Vec<Vec<bool>>) -> usize {
+    let mut square_count: usize = 0;
+
+    for j in 0..matrix.len() {
+        for i in 0..matrix[0].len() {
+            if matrix[i][j] == true {}
+        }
+    }
+
+    square_count
+}
+
+fn does_matrix_square_at(matrix: &Vec<Vec<bool>>) -> bool {}
+
+/*
+ * Mirror number
+ */
+pub fn mirror_number(mut value: u32) -> u32 {
+    const BASE: u32 = 10;
+
+    let mut mirror: u32 = 0;
+    let size = value.to_string().len();
+
+    for index in 1..=size {
+        let last = value % BASE;
+        value = value / BASE;
+        mirror += last * BASE.pow(size as u32 - index as u32);
+    }
+
+    mirror
+}
+
+pub fn mirror_number_lazy(value: u32) -> u32 {
+    value
+        .to_string()
+        .chars()
+        .rev()
+        .collect::<String>()
+        .parse::<u32>()
+        .unwrap()
+}
+
+pub fn longest_palindrome(value: &str) -> String {
+    let mut lp: String = "0".to_string();
+    let input_size = value.len() - 1;
+
+    for pal_size in 2..=input_size {
+        for i in 0..input_size {
+            if input_size - i < pal_size {
+                break;
+            }
+            if let Some(slice) = value.get(i..(i + pal_size - 1)) {
+                // if string was mutable, we count use .reserve()
+                let reverted_slice = slice.chars().rev().collect::<String>();
+                if slice == reverted_slice {
+                    lp = reverted_slice;
+                    break;
+                }
+            }
+        }
+    }
+
+    lp
+}
+
+/*
+ * Quick sort
+ */
+pub fn quick_sort<T>(list: Vec<T>) -> Vec<T>
+where
+    T: PartialOrd + Copy,
+{
+    if list.is_empty() {
+        return list;
+    }
+    let mut pivot_list = vec![list[0]];
+    let pivot = pivot_list[0];
+    // arrange
+    let mut left_list: Vec<T> = Vec::new();
+    let mut right_list: Vec<T> = Vec::new();
+    for index in 1..list.len() {
+        let element = list[index];
+        if element > pivot {
+            right_list.push(element);
+        } else if element < pivot {
+            left_list.push(element);
+        } else {
+            pivot_list.push(element);
+        }
+    }
+
+    left_list = quick_sort(left_list);
+    right_list = quick_sort(right_list);
+    left_list.append(&mut pivot_list);
+    left_list.append(&mut right_list);
+
+    left_list
+}

src/exercises/mod.rs

@@ -0,0 +1,77 @@
+use std::time::Instant;
+
+mod easy_difficulty;
+mod hard_difficulty;
+mod medium_difficulty;
+
+pub fn run_hard() {
+    println!();
+}
+
+pub fn run_medium() {
+    println!(
+        "Longest palindrome of 'asdffdas' is {}",
+        medium_difficulty::longest_palindrome("asdffdas")
+    );
+
+    let to_mirror = 12345u32;
+
+    let begin = Instant::now();
+    println!(
+        "The mirror of {} is {} and took {:?}",
+        to_mirror,
+        medium_difficulty::mirror_number(to_mirror),
+        begin.elapsed()
+    );
+
+    let begin = Instant::now();
+    println!(
+        "(lazy) The mirror of {} is {} and took {:?}",
+        to_mirror,
+        medium_difficulty::mirror_number_lazy(to_mirror),
+        begin.elapsed()
+    );
+
+    let boolean_matrix = vec![
+        vec![true, false, true, true],
+        vec![false, false, true, true],
+    ];
+    println!(
+        "The matrix:\n{:?}\nhas {} squares inside",
+        boolean_matrix,
+        medium_difficulty::count_squares(&boolean_matrix)
+    );
+}
+
+pub fn run_easy() {
+    let list = vec![5, 1, 8, 20, 4];
+    // easy_difficulty::binary_search(list, 20);
+    // let list = easy_difficulty::slow_sort_list(list);
+    // println!("List ordered to {:?}", list);
+    println!(
+        "The vec {:?} is {} sorted, but [1,2,3,4] is {} sorted",
+        list,
+        easy_difficulty::is_sorted(&list),
+        easy_difficulty::is_sorted(&[1, 2, 3, 4])
+    );
+
+    let sorted_list = vec![1, 10, 15, 20, 30];
+    let searched = 40;
+    let position = easy_difficulty::binary_search(&sorted_list, searched);
+    match position {
+        Ok(pos) => println!(
+            "The element {searched} is indexed in {pos} at {:?}",
+            sorted_list
+        ),
+        Err(e) => println!("Error: {}", e),
+    }
+
+    let bubled_list = easy_difficulty::bubble_sort(list);
+    println!("The original list sorted is {:?}", bubled_list);
+
+    let long_list = vec![
+        5, 1, 8, 20, 4, 15, 6, 7, 1, 4, 23, 9, 23, 5, 7, 7, 8, 0, 12, 4, 56, 18, 47, 23,
+    ];
+    let sorted_list = medium_difficulty::quick_sort(long_list);
+    println!("The sorted list is: {:?}", sorted_list);
+}

src/functions.rs

@@ -0,0 +1,117 @@
+fn fizzbuzz(n: i32) {
+    for i in 1..=n {
+        if i % 15 == 0 {
+            println!("FizzBuzz");
+        } else if i % 5 == 0 {
+            println!("Buzz");
+        } else if i % 3 == 0 {
+            println!("Fizz");
+        } else {
+            println!("{i}");
+        }
+    }
+}
+
+// Associated functions (without self) and Methods (with self)
+// are the ways of connecting a function to a type.
+struct Point {
+    x: i8,
+    y: i8,
+}
+
+impl Point {
+    // Associated functions
+    fn origin() -> Point {
+        Point { x: 0, y: 0 }
+    }
+
+    fn new(x: i8, y: i8) -> Point {
+        Point { x, y }
+    }
+
+    // Methods
+    fn run(&mut self, x: i8, y: i8) {
+        self.x += x;
+        self.y += y;
+    }
+
+    // bad practice, just for practice
+    fn to_string(&self) -> String {
+        format!("{} {}", self.x, self.y)
+    }
+}
+
+// when used as a parameter in a function
+// the closures complete type must be annotated using one of a few traits.
+// In order to decrease restriction, they are:
+// Fn: the closure uses the captured value by reference (&T)
+// FnMut: the closure uses the captured value by mutable reference (&mut T)
+// FnOnce: the closure uses the captured value by value (T)
+//
+// NOTE: this function could also take a normal function as a parameter, not only a closure
+fn apply<F>(f: F)
+where
+    F: FnOnce(),
+{
+    println!("About to run a closure...");
+    f();
+}
+
+fn create_fn() -> impl Fn() {
+    let text = "Fn".to_owned();
+    move || println!("Info: {}", text) // move converts the used variables to variables captured by
+                                       // value;
+}
+
+fn divergin_one() -> ! {
+    panic!("This will never return! PANIC");
+}
+
+pub fn functions_module() {
+    fizzbuzz(10);
+
+    println!("-- Associated functions and Methods --");
+
+    let mut my_point = Point::new(4, 5);
+    println!("My point: {}", my_point.to_string());
+
+    my_point.run(20, 1);
+    println!("My point: {}", my_point.to_string());
+
+    // Closures are made to allow access to the enclosing environment,
+    // similar to JS functions inside functions
+    let mut closure_run = |x: i8, y: i8| {
+        my_point.x += x;
+        my_point.y += y;
+    };
+
+    closure_run(10, 15);
+    println!("My point: {}", my_point.to_string());
+    // closure_run(10, 15);
+    // println!("My point: {}", my_point.to_string());
+
+    // move keyword forces the closure to take ownership of captured variables
+    let mut closure_run = move |x: i8, y: i8| {
+        my_point.x += x;
+        my_point.y += y;
+    };
+
+    // Rust provides higher order functions, such as
+    // - map : .map(|n| n * n)
+    // - filter : .filter(|&n| is_add(n))
+    // - take_while : .take_while(|&n| n < upper)
+
+    // Diverging functions
+    // Never return, marked with: !
+    // Useful on divergin situations where an exact type is required
+    for i in 0..5 {
+        let value: u32 = match i % 2 == 0 {
+            true => 5,
+            false => continue,
+        };
+        println!("The value is pair and {value}");
+    }
+
+    // NOTE: Bad example since it's not really useful
+    divergin_one();
+}

src/macros.rs

@@ -0,0 +1,103 @@
+// Group functionality with different types
+// Define special syntac for specific purpose
+// Variable number of arguments
+// Different combination of arguments
+macro_rules! say_hello {
+    () => {
+        println!("Hello world!");
+    };
+}
+
+// Types of arguments have designators:
+// block
+// expr is used for expressions
+// ident is used for variable/function names
+// item
+// literal is used for literal constants
+// pat (pattern)
+// path
+// stmt (statement)
+// tt (token tree)
+// ty (type)
+// vis (visibility qualifier)
+macro_rules! generate_function {
+    ($func_name:ident) => {
+        fn $func_name() {
+            println!("You called {:?}()", stringify!($func_name));
+        }
+    };
+}
+
+generate_function!(foo);
+
+macro_rules! process_expression {
+    ($expression: expr) => {
+        println!("{:?} = {:?}", stringify!($expression), $expression);
+    };
+}
+
+// Overload
+macro_rules! match_block {
+    ($left: expr; and $right: expr) => {
+        println!("A: {:?} and {:?}", stringify!($left), stringify!($right))
+    };
+
+    ($left: expr; or $right:expr) => {
+        println!(
+            "B: {:?} or {:?} is {:?}",
+            stringify!($left),
+            stringify!($right),
+            $left || $right
+        )
+    };
+}
+
+// Repeat: variable number of args o a type
+macro_rules! find_max {
+    ($x:expr) => ($x);
+    ($x:expr, $($y:expr), +) => (std::cmp::max($x, find_max!($($y), +)));
+}
+
+// DSLs: Domain Specific Languages
+// macro_rules allows you to create your own syntax
+macro_rules! calc {
+    (eval $e:expr) => {
+        println!("{} = {}", stringify!($e), $e);
+    };
+}
+
+macro_rules! calculate {
+    (eval $e: expr) => {
+        {
+            let val: usize = $e; // Force types to be integers
+            println!("{} = {}", stringify!{$e}, val);
+        }
+    };
+    (eval $e: expr, $(eval $y: expr), +) => {{
+        calculate!{eval $e}
+        calculate!{ $(eval $y), + }
+    }};
+}
+
+pub fn macros_rule() {
+    foo();
+    say_hello!();
+    process_expression!(1 + 5 * 3);
+
+    match_block!(1i32 + 1 == 2i32; and 2i32 * 2 == 4i32); // Enters first branch
+    match_block!(true; or false); // Enter second branch
+    match_block!(true; and true); // Enters first branch
+
+    println!("Max is {}", find_max!(5, 3 * 8, 4, 9 * 5));
+
+    calc! {
+        eval (1 + 2) * 4
+    }
+
+    calculate! {
+        eval (1 + 2) * 4,
+        eval 1 + 5,
+        eval 7 + 4,
+        eval 3 + 9
+    }
+}

src/main.rs

@@ -5,15 +5,11 @@
 // : /// Doc comment: generate library docs for the following item
 // : //! Doc comment
 
-// mod helloworld;
+mod threads;
-// mod primitives;
+
-// mod customtypes;
+#[cfg(test)]
-//mod variablebindings;
+#[path = "./test/basic_test.rs"]
-// mod types;
+mod test;
-//mod conversion;
-// mod controlflow;
-// mod traits;
-mod str_types;
 
 fn main() {
     // helloworld::hello_world_module();
@@ -23,6 +19,15 @@ fn main() {
     //types::types_module();
     //conversion::conversion_module();
     // controlflow::control_flow_module();
-    //traits::traits_exercise();
+    // traits::traits_exercise();
-    str_types::str_types_module();
+    // str_types::str_types_module();
+    // my_lib::public_function();
+    // functions::functions_module();
+    // concepts::box_basics();
+    // operators::operators_module();
+    // macros_rule();
+
+    // exercises::run_easy();
+    // exercises::run_medium();
+    threads::threads_module();
 }

src/my_lib.rs

@@ -0,0 +1,8 @@
+pub fn public_function() {
+    println!("This is a public funcion that calls a private one!");
+    private_function();
+}
+
+fn private_function() {
+    println!("This is a private function!");
+}

src/operators.rs

@@ -0,0 +1,24 @@
+use std::ops;
+use std::ops::Add;
+
+/*
+ * Operators are syntectic sugar for method calls
+ * The + operator calls the add method and so on
+ * */
+pub fn operators_module() {
+    let a = 3u32.add(3);
+    println!("a is {a}");
+
+    // Operator overloading
+    struct Foo;
+    impl ops::Add<u32> for Foo {
+        type Output = Foo;
+        fn add(self, rhs: u32) -> Self::Output {
+            println!("> add called with {}", rhs);
+            Foo
+        }
+    }
+
+    let foo = Foo;
+    let _too = foo + 3; // > add called with 3
+}

src/test/basic_test.rs

@@ -0,0 +1,14 @@
+#[cfg(test)]
+pub mod tests {
+    #[test]
+    fn test_success() {
+        let my_hello = "Hello world!";
+        assert_eq!(my_hello, "Hello world!");
+    }
+
+    #[test]
+    fn test_failure() {
+        let my_hello = "ef u world!";
+        assert_eq!(my_hello, "Hello world!");
+    }
+}

src/threads.rs

@@ -0,0 +1,68 @@
+use std::{thread, time::Instant};
+
+use rand::Rng;
+
+const NTHREADS: u32 = 6;
+
+fn generate_number_block(size: usize) -> String {
+    let mut block = String::new();
+    for _ in 0..size {
+        block.push_str(&rand::rng().random_range(0..9).to_string());
+    }
+    block
+}
+
+pub fn threads_module() {
+    let number_block = generate_number_block(999999);
+
+    let time = Instant::now();
+    let result_base = sum_of_block(&number_block);
+    let elapsed_base = time.elapsed();
+    println!("Functional took {}", elapsed_base.as_micros());
+
+    let time = Instant::now();
+    let result_parallel = sum_of_block_parallel(&number_block, 10);
+    let elapsed_parallel = time.elapsed();
+    println!("Parallel took {}", elapsed_parallel.as_micros());
+
+    if result_base == result_parallel {
+        println!(
+            "The results are the same ({}) and the time difference is {}",
+            result_base,
+            elapsed_parallel.as_micros() - elapsed_base.as_micros()
+        )
+    } else {
+        println!("One is wrong...");
+    }
+}
+
+fn sum_of_block_parallel(digits: &str, nthreads: usize) -> u32 {
+    let digits = digits.split_at(digits.len() / 2);
+    3
+}
+
+fn sum_of_block(digits: &str) -> u32 {
+    digits
+        .chars()
+        .into_iter()
+        .map(|character| character.to_digit(10).unwrap())
+        .sum::<u32>()
+}
+
+fn basic_thread_wait() {
+    let mut thread_list = vec![];
+    for i in 0..NTHREADS {
+        thread_list.push(thread::spawn(move || {
+            println!("this is the thread {}", i);
+            return 1;
+        }));
+    }
+
+    for th in thread_list {
+        let result = th.join();
+        match result {
+            Ok(r) => println!("Thread finished! {:?}", r),
+            Err(e) => println!("Thread error {:?}", e),
+        }
+    }
+}

src/traits.rs

@@ -6,6 +6,8 @@
  * 4. Extend the trait with a second function and see what happens
  * */
 
+use std::thread::current;
+
 pub trait Move {
     fn to(&mut self, x: i32, y: i32);
 }
@@ -32,4 +34,91 @@ pub fn traits_exercise() {
     me.to(10, 20);
 
     println!("My name is {} and i'm at {:?}", me.name, me.position);
+
+    // Drop trait: called with an object goes out of scope
+    struct Foo;
+    impl Drop for Foo {
+        fn drop(&mut self) {
+            println!("Foo went out of scope...");
+        }
+    }
+
+    let mut counter = 0u32;
+    loop {
+        if counter > 5 {
+            break;
+        }
+        counter += 1;
+        let _foo = Foo;
+    }
+
+    // Iterator traits
+    // Example: Fibonacci
+    struct Fibonacci {
+        current: u32,
+        next: u32,
+    }
+
+    impl Iterator for Fibonacci {
+        type Item = u32;
+        fn next(&mut self) -> Option<Self::Item> {
+            let current = self.current;
+            self.current = self.next;
+            self.next = self.next + current;
+            Some(current)
+        }
+    }
+
+    let mut fib = Fibonacci {
+        current: 0,
+        next: 1,
+    };
+
+    for _ in 0..21 {
+        println!("Fib {:?}", fib.next());
+    }
+
+    let mut fib = Fibonacci {
+        current: 0,
+        next: 1,
+    };
+    println!("Fib 20 {:?}", fib.nth(20));
+    let fib = Fibonacci {
+        current: 0,
+        next: 1,
+    };
+    println!("Fib skip 20 {:?}", fib.skip(20).next());
+
+    // Disambiguating overlapping traits
+    struct Fee {
+        a: u32,
+        b: String,
+    }
+
+    trait A {
+        fn get(&self) -> u32;
+    }
+    trait B {
+        fn get(&self) -> String;
+    }
+
+    impl A for Fee {
+        fn get(&self) -> u32 {
+            self.a
+        }
+    }
+    impl B for Fee {
+        fn get(&self) -> String {
+            self.b.clone()
+        }
+    }
+
+    let fee = Fee {
+        a: 1234,
+        b: "asdf".to_string(),
+    };
+
+    let a = <Fee as A>::get(&fee);
+    let b = <Fee as B>::get(&fee);
+    println!("The a is {} and the b is {}", a, b);
 }