add chapter [Debug and Display]

solutions/formatted-output/debug-display.md

@@ -0,0 +1,78 @@
+1.
+```rust
+#[derive(Debug)]
+struct Structure(i32);
+
+fn main() {
+    // Types in std and Rust have implemented the fmt::Debug trait
+    println!("{:?} months in a year.", 12);
+
+    println!("Now {:?} will print!", Structure(3));
+}
+```
+2.
+```rust
+#[derive(Debug)]
+struct Person {
+    name: String,
+    age: u8
+}
+
+fn main() {
+    let person = Person { name:  "Sunface".to_string(), age: 18 };
+
+    println!("{:#?}", person);
+}
+```
+
+3.
+```rust
+use std::fmt;
+
+struct Structure(i32);
+
+struct Deep(Structure);
+impl fmt::Debug for Deep {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?}", self.0.0)
+    }
+}
+
+fn main() {    
+    // The problem with `derive` is there is no control over how
+    // the results look. What if I want this to just show a `7`?
+
+    /* Make it output: Now 7 will print! */
+    println!("Now {:?} will print!", Deep(Structure(7)));
+}
+```
+
+4
+```rust
+use std::fmt;
+
+struct Point2D {
+    x: f64,
+    y: f64,
+}
+
+impl fmt::Display for Point2D {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Display: {} + {}i", self.x, self.y)
+    }
+}
+
+impl fmt::Debug for Point2D {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Debug: Complex {{ real: {:?}, imag: {:?} }}", self.x, self.y)
+    }
+}
+
+fn main() {
+
+    let point = Point2D { x: 3.3, y: 7.2 };
+    println!("{}", point);
+
+    println!("{:?}", point);
+}
+```