Added program to teach writing display functions

display.rs

@@ -0,0 +1,71 @@
+use std::fmt;	//Import `fmt`
+
+//A structure holding two numbers. `Debug` will be derived so the results can
+//be contrasted with `Display`.
+#[derive(Debug)]
+struct MinMax(i64, i64);
+//Implement `Display` for `MinMax`.
+impl fmt::Display for MinMax{
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result{
+		//Use `self.number` to refer to each positional data point.
+		write!(f, "({}, {})", self.0, self.1)
+	}
+}
+
+//Define a structure where the fields are nameable for comparison.
+#[derive(Debug)]
+struct Point2D{
+	x: f64,
+	y: f64,
+}
+//Similarly, implement `Display` for `Point2D`
+impl fmt::Display for Point2D{
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result{
+		//Customize so only `x` and `y` are denoted.
+		write!(f, "x: {}, y: {}", self.x, self.y)
+	}
+}
+
+//Define a structure for complex numbers
+#[derive(Debug)]
+struct Complex{
+	real: f64,
+	imag: f64,
+}
+//Implement 'Display' for Complex
+impl fmt::Display for Complex{
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result{
+		write!(f, "{} + {}i", self.real, self.imag)
+	}
+}
+
+fn main(){
+	let minmax = MinMax(0, 14);
+
+	println!("Compare structures:");
+	println!("Display: {}", minmax);
+	println!("Debug: {:?}", minmax);
+
+	let big_range =   MinMax(-300, 300);
+	let small_range = MinMax(-3, 3);
+
+	println!("The big range is {big} and the small is {small}",
+			 small = small_range,
+			 big = big_range);
+
+	let point = Point2D { x: 3.3, y: 7.2 };
+
+	println!("Compare points:");
+	println!("Display: {}", point);
+	println!("Debug: {:?}", point);
+
+	//Error. Both `Debug` and `Display` were implemented, but `{:b}`
+	//requires `fmt::Binary` to be implemented. This will not work.
+	//println!("What does Point2D look like in binary: {:b}?", point);
+
+	//Print a test for Complex
+	let comp = Complex{real: 3.3, imag: 7.2};
+	println!("Compare Complex:");
+	println!("Display: {}", comp);
+	println!("debug: {:?}", comp);
+}