[Add] exercises/options

exercises/options/options1.rs

@@ -1,16 +1,15 @@
 // options1.rs
 // Execute `rustlings hint options1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 // This function returns how much icecream there is left in the fridge.
 // If it's before 10PM, there's 5 pieces left. At 10PM, someone eats them
 // all, so there'll be no more left :(
 fn maybe_icecream(time_of_day: u16) -> Option<u16> {
-    // We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a value of 0
-    // The Option output should gracefully handle cases where time_of_day > 23.
-    // TODO: Complete the function body - remember to return an Option!
-    ???
+    match time_of_day {
+        0..=21 => Some(5),
+        22..=23 => Some(0),
+        _ => None
+    }
 }
 
 #[cfg(test)]
@@ -28,8 +27,7 @@ mod tests {
 
     #[test]
     fn raw_value() {
-        // TODO: Fix this test. How do you get at the value contained in the Option?
-        let icecreams = maybe_icecream(12);
+        let icecreams = maybe_icecream(12).unwrap();
         assert_eq!(icecreams, 5);
     }
 }

exercises/options/options2.rs

@@ -1,8 +1,6 @@
 // options2.rs
 // Execute `rustlings hint options2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -12,8 +10,7 @@ mod tests {
         let target = "rustlings";
         let optional_target = Some(target);
 
-        // TODO: Make this an if let statement whose value is "Some" type
-        word = optional_target {
+        if let Some(word) = optional_target {
             assert_eq!(word, target);
         }
     }
@@ -26,10 +23,8 @@ mod tests {
             optional_integers.push(Some(i));
         }
 
-        // TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>
-        // You can stack `Option<T>`'s into while let and if let
-        integer = optional_integers.pop() {
-            assert_eq!(integer, range);
+        while let Some(integer) = optional_integers.pop() {
+            assert_eq!(integer, Some(range));
             range -= 1;
         }
     }

exercises/options/options3.rs

@@ -1,8 +1,6 @@
 // options3.rs
 // Execute `rustlings hint options3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 struct Point {
     x: i32,
     y: i32,
@@ -12,7 +10,7 @@ fn main() {
     let y: Option<Point> = Some(Point { x: 100, y: 200 });
 
     match y {
-        Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
+        Some(ref p) => println!("Co-ordinates are {},{} ", p.x, p.y),
         _ => println!("no match"),
     }
     y; // Fix without deleting this line.