✨add new exercise

dev/Cargo.toml

@@ -100,6 +100,8 @@ bin = [
   { name = "options2_sol", path = "../solutions/12_options/options2.rs" },
   { name = "options3", path = "../exercises/12_options/options3.rs" },
   { name = "options3_sol", path = "../solutions/12_options/options3.rs" },
+  { name = "options4", path = "../exercises/12_options/options4.rs" },
+  { name = "options4_sol", path = "../solutions/12_options/options4.rs" },
   { name = "errors1", path = "../exercises/13_error_handling/errors1.rs" },
   { name = "errors1_sol", path = "../solutions/13_error_handling/errors1.rs" },
   { name = "errors2", path = "../exercises/13_error_handling/errors2.rs" },

exercises/12_options/options4.rs

@@ -0,0 +1,46 @@
+#[derive(Debug)]
+struct Point {
+    x: i32,
+    y: i32,
+}
+
+fn main() {
+    let optional_point = Some(Point { x: 100, y: 200 });
+
+    // Exercise 1: Use ok_or to convert optional_point to a Result.
+    // If the point exists, print its coordinates.
+    // If it doesn't, print the error message "Point does not exist".
+    // TODO: Fix the match statement to handle Result properly.
+
+    let result_point = optional_point.ok_or(???);
+    match result_point {
+        Ok(p) => println!("Co-ordinates are {},{}", p.x, p.y),
+        Err(e) => println!("{}", e),
+    }
+
+    // Exercise 2: Use ok_or_else to achieve the same functionality as above,
+    // but with a closure to generate the error message.
+    // TODO: Fix the match statement to handle Result properly.
+    let result_point_else = optional_point.ok_or_else(???);
+    match result_point_else {
+        Ok(p) => println!("Co-ordinates are {},{}", p.x, p.y),
+        Err(e) => println!("{}", e),
+    }
+
+    // Exercise 3: Use and_then to chain operations on optional_point.
+    // If the point exists, compute the distance from the origin and return it as an Option.
+    // If it doesn't, return None.
+    let distance_from_origin = optional_point.and_then(
+        ???{
+        let distance = ((p.x.pow(2) + p.y.pow(2)) as f64).sqrt();
+        Some(distance)
+    }
+    );
+    // TODO: Fix the match statement to handle Option properly.
+    match distance_from_origin {
+        Some(distance) => println!("Distance from origin is {:.2}", distance),
+        None => println!("No point to calculate distance"),
+    }
+
+    println!("{optional_point:?}"); // Don't change this line.
+}

rustlings-macros/info.toml

@@ -627,6 +627,25 @@ After making the correction as suggested by the compiler, read the related docs
 page:
 https://doc.rust-lang.org/std/keyword.ref.html"""
 
+[[exercises]]
+name = "options4"
+dir = "12_options"
+test = false
+hint = """
+Exercise 1:
+
+Hint: Use the ok_or method to convert the Option<Point> to a Result<Point, &str>. Handle the Ok case to print the coordinates and the Err case to print the error message.
+Example: optional_point.ok_or("Point does not exist")
+Exercise 2:
+
+Hint: Use the ok_or_else method to convert the Option<Point> to a Result<Point, &str>, similar to ok_or but using a closure to generate the error message.
+Example: optional_point.ok_or_else(|| "Point does not exist")
+Exercise 3:
+
+Hint: Use the and_then method to chain the operation of calculating the distance from the origin. This method should only execute if optional_point is Some.
+Example: optional_point.and_then(|p| { let distance = ((p.x.pow(2) + p.y.pow(2)) as f64).sqrt(); Some(distance) })
+"""
+
 # ERROR HANDLING
 
 [[exercises]]

solutions/12_options/options4.rs

@@ -0,0 +1,40 @@
+#[derive(Debug)]
+struct Point {
+    x: i32,
+    y: i32,
+}
+
+fn main() {
+    let optional_point = Some(Point { x: 100, y: 200 });
+
+    // Exercise 1: Use ok_or to convert optional_point to a Result.
+    // If the point exists, print its coordinates.
+    // If it doesn't, print the error message "Point does not exist".
+    let result_point = optional_point.ok_or("Point does not exist");
+    match result_point {
+        Ok(p) => println!("Co-ordinates are {},{}", p.x, p.y),
+        Err(e) => println!("{}", e),
+    }
+
+    // Exercise 2: Use ok_or_else to achieve the same functionality as above,
+    // but with a closure to generate the error message.
+    let result_point_else = optional_point.ok_or_else(|| "Point does not exist");
+    match result_point_else {
+        Ok(p) => println!("Co-ordinates are {},{}", p.x, p.y),
+        Err(e) => println!("{}", e),
+    }
+
+    // Exercise 3: Use and_then to chain operations on optional_point.
+    // If the point exists, compute the distance from the origin and return it as an Option.
+    // If it doesn't, return None.
+    let distance_from_origin = optional_point.and_then(|p| {
+        let distance = ((p.x.pow(2) + p.y.pow(2)) as f64).sqrt();
+        Some(distance)
+    });
+    match distance_from_origin {
+        Some(distance) => println!("Distance from origin is {:.2}", distance),
+        None => println!("No point to calculate distance"),
+    }
+
+    println!("{optional_point:?}"); // Don't change this line.
+}