add chapter [formatting]

solutions/formatted-output/formatting.md

@@ -0,0 +1,140 @@
+1.
+```rust
+fn main() {
+    println!("{0}, this is {1}. {1}, this is {0}", "Alice", "Bob");// => Alice, this is Bob. Bob, this is Alice
+    assert_eq!(format!("{1}{0}", 1, 2), "21");
+    assert_eq!(format!("{1}{}{0}{}", 1, 2), "2112");
+    println!("Success!")
+}
+```
+
+2.
+```rust
+fn main() {
+    println!("{argument}", argument = "test"); // => "test"
+
+    assert_eq!(format!("{name}{}", 1, name = 2), "21");
+    assert_eq!(format!("{a} {c} {b}",a = "a", b = 'b', c = 3 ), "a 3 b");
+    
+    // named argument must be placed after other arguments
+    println!("{abc} {0}", 2, abc = "def");
+
+    println!("Success!")
+}
+```
+
+3.
+```rust
+fn main() {
+    // the following two are padding with 5 spaces
+    println!("Hello {:5}!", "x"); // =>  "Hello x    !"  
+    println!("Hello {:1$}!", "x", 5); // =>  "Hello x    !"
+
+    assert_eq!(format!("Hello {1:0$}!", 5, "x"), "Hello x    !");
+    assert_eq!(format!("Hello {:width$}!", "x", width = 5), "Hello x    !");
+
+    println!("Success!")
+}
+```
+
+4.
+```rust
+fn main() {
+    // left align
+    println!("Hello {:<5}!", "x"); // => Hello x    !
+    // right align
+    assert_eq!(format!("Hello {:>5}!", "x"), "Hello     x!");
+    // center align
+    assert_eq!(format!("Hello {:^5}!", "x"), "Hello   x  !");
+
+    // left align, pad with '&'
+    assert_eq!(format!("Hello {:&<5}!", "x"), "Hello x&&&&!");
+
+    println!("Success!")
+}
+```
+
+5.
+```rust
+fn main() {
+    println!("Hello {:5}!", 5); // => Hello     5!
+    println!("Hello {:+}!", 5); // =>  Hello +5!
+    println!("Hello {:05}!", 5); // => Hello 00005!
+    println!("Hello {:05}!", -5); // => Hello -0005!
+
+    assert!(format!("{number:0>width$}", number=1, width=6) == "000001");
+    
+    println!("Success!")
+}
+```
+
+6.
+```rust
+fn main() {
+    let v = 3.1415926;
+
+    println!("{:.1$}", v, 4); // same as {:.4} => 3.1416 
+
+    assert_eq!(format!("{:.2}", v), "3.14");
+    assert_eq!(format!("{:+.2}", v), "+3.14");
+    assert_eq!(format!("{:.0}", v), "3");
+
+    println!("Success!")
+}
+```
+
+7.
+```rust
+fn main() {
+    let s = "Hello, world!";
+
+    println!("{0:.5}", s); // => Hello
+
+    assert_eq!(format!("Hello {1:.0$}!", 3, "abcdefg"), "Hello abc!");
+
+    println!("Success!")
+}
+```
+
+8.
+```rust
+fn main() {
+     assert_eq!(format!("{:#b}", 27), "0b11011");
+     assert_eq!(format!("{:#o}", 27), "0o33");
+     assert_eq!(format!("{:#x}", 27), "0x1b");
+     assert_eq!(format!("{:#X}", 27), "0x1B");
+
+     println!("{:x}!", 27); // hex with no prefix => 1b
+ 
+     println!("{:#010b}", 27); // pad binary with 0, width = 10,  => 0b00011011
+
+    println!("Success!")
+}
+```
+
+9.
+```rust
+fn get_person() -> String {
+    String::from("sunface")
+}
+
+fn get_format() -> (usize, usize) {
+    (4, 1)
+}
+
+
+fn main() {
+    let person = get_person();
+    println!("Hello, {person}!");
+
+    let (width, precision) = get_format();
+    let scores = [("sunface", 99.12), ("jack", 60.34)];
+    /* Make it print:
+    sunface:   99.1
+    jack:   60.3
+    */
+    for (name, score) in scores {
+        println!("{name}: {score:width$.precision$}");
+    }
+}
+```