Chapter 8: Common collections

src/main.rs

@@ -9,6 +9,7 @@ fn main() {
     chapter_5();
     chapter_6();
     chapter_7();
+    chapter_8();
 }
 
 fn chapter_1() {
@@ -825,3 +826,173 @@ use foo::{
     bar::{self, Foo},
     baz::{*, quux::Bar},
 };
+
+fn chapter_8() {
+    println!("Chapter 8: Common collections");
+    vectors();
+    strings();
+    hash_maps();
+
+    println!("Exercice time 😺");
+
+    println!();
+}
+
+fn vectors() {
+    println!("Vectors");
+    let mut v = vec![1, 2, 3];
+    v.push(4);
+
+    {
+        // let does_not_exist = &v[100];    // panic
+        let does_not_exist = v.get(100);    // Option<&T>
+        println!("We can get a vector value with `&v[i]` or `v.get(i)`: {:?}", does_not_exist);
+    }
+
+    for i in &v {
+        println!("{}", i);
+    }
+
+    for i in &mut v {
+        *i += 50;
+    }
+
+    for i in &v {
+        println!("{}", i);
+    }
+
+    #[derive(Debug)]
+    enum SpreadsheetCell {
+        Int(i32),
+        Float(f64),
+        Text(String),
+    }
+    let row = vec![
+        SpreadsheetCell::Int(3),
+        SpreadsheetCell::Text(String::from("blue")),
+        SpreadsheetCell::Float(13.37),
+    ];
+
+    println!("To have multiples types inside a vector we should use an enum: {:?}.", row);
+
+    println!();
+}
+
+fn strings() {
+    let hello = String::from("السلام عليكم");
+    println!("Hello: {}", hello);
+    let hello = String::from("Dobrý den");
+    println!("Hello: {}", hello);
+    let hello = String::from("Hello");
+    println!("Hello: {}", hello);
+    let hello = String::from("שָׁלוֹם");
+    println!("Hello: {}", hello);
+    let hello = String::from("नमस्ते");
+    println!("Hello: {}", hello);
+    let hello = String::from("こんにちは");
+    println!("Hello: {}", hello);
+    let hello = String::from("안녕하세요");
+    println!("Hello: {}", hello);
+    let hello = String::from("你好");
+    println!("Hello: {}", hello);
+    let hello = String::from("Olá");
+    println!("Hello: {}", hello);
+    let hello = String::from("Здравствуйте");
+    println!("Hello: {}", hello);
+    let hello = String::from("Hola");
+    println!("Hello: {}", hello);
+
+    let s1 = String::from("Hello, ");
+    let s2 = String::from("world!");
+    let s3 = s1 + &s2;
+    println!("s1 is moved and not usable anymore, s2: {}, s3: {}", /*s1, */s2, s3);
+    let s2 = String::from("tac");
+
+    let s1 = String::from("tic");
+    let s3 = String::from("toe");
+
+    let s = s1 + "-" + &s2 + "-" + &s3;
+    println!("s: {}", s);
+
+    let s1 = String::from("tic");   // s1 was moved because of the `+` operator
+
+    let s = format!("{}-{}-{}", s1, s2, s3);
+    println!("s: {}, s1 {}, s2 {}, s3 {}", s, s1, s2, s3);  // here no String is moved
+
+    println!("We cannot use index on Strings but we can refer to a range.");
+    println!("But we should be carefull with the ranges to not split a 2byte unicode char.");
+
+    let hindi_2bytes_with_modifiers = "नमस्ते";
+
+    println!("Individuals bytes:");
+    for b in hindi_2bytes_with_modifiers.bytes() {
+        println!("{}", b);
+    }
+
+    println!("Individuals UTF-8 chars. Note the modifier (accents, ...) may be separated from the naked character.");
+    for c in hindi_2bytes_with_modifiers.chars() {
+        println!("{}", c);
+    }
+
+    println!("If we want the human characteres insteads of the UTF-8 ones -> https://crates.io/");
+
+    println!();
+}
+
+fn hash_maps() {
+    use std::collections::HashMap;
+
+    let mut scores = HashMap::new();
+
+    scores.insert(String::from("Blue"), 10);
+    scores.insert(String::from("Yellow"), 50);
+
+    println!("Scores: {:?}", scores);
+
+    let teams = vec![String::from("Blue"), String::from("Yellow")];
+    let initial_scores = vec![10, 50];
+
+    let scores_tuple = teams.iter().zip(initial_scores.iter());
+    println!("Scores tuple: {:?} (Intermediate not necessary, just to see what is happening)", scores_tuple);
+
+    let scores: HashMap<_, _> = scores_tuple.collect();
+    println!("Scores: {:?}", scores);
+
+    let team_name = String::from("Blue");
+    match scores.get(&team_name) {
+        Some(sc) => println!("{} team score is: {}", &team_name, sc),
+        None => println!("No score for team: {}", &team_name),
+    }
+
+    for (key, value) in &scores {
+        println!("{}: {}", key, value);
+    }
+
+    let mut scores = HashMap::new();
+
+    scores.insert(String::from("Blue"), 10);
+    scores.insert(String::from("Yellow"), 50);
+
+    scores.insert(String::from("Blue"), 25);    // Overwriting a value
+
+    for (key, value) in &scores {
+        println!("{}: {}", key, value);
+    }
+
+    scores.entry(String::from("Blue")).or_insert(50); // Only insert if the value does not exist
+    scores.entry(String::from("Red")).or_insert(50);
+    println!("{:?}", scores);
+
+    let text = "hello world wonderful world";
+    let mut map = HashMap::new();
+
+    for word in text.split_whitespace() {
+        let count = map.entry(word).or_insert(0);
+        *count += 1;
+    }
+    println!("{:?}", map);
+
+    println!("The hashing function is cryptographically secure. If it's slow, use an other one implementing the `BuildHasher` trait.");
+
+    println!();
+}