feat: 🎸 added error handling exercises

exercises/error_handling/errors1.rs

@@ -5,14 +5,12 @@
 // construct to `Option` that can be used to express error conditions. Let's use it!
 // Execute `rustlings hint errors1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
-pub fn generate_nametag_text(name: String) -> Option<String> {
+pub fn generate_nametag_text(name: String) -> Result<String, String> {
     if name.is_empty() {
         // Empty names aren't allowed.
-        None
+        Err(String::from("`name` was empty; it must be nonempty."))
     } else {
-        Some(format!("Hi! My name is {}", name))
+        Ok(format!("Hi! My name is {}", name))
     }
 }
 

exercises/error_handling/errors2.rs

@@ -17,16 +17,15 @@
 // one is a lot shorter!
 // Execute `rustlings hint errors2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
 
 pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
     let processing_fee = 1;
     let cost_per_item = 5;
-    let qty = item_quantity.parse::<i32>();
+    let qty = item_quantity.parse::<i32>()?;
 
-    Ok(qty * cost_per_item + processing_fee)
+    let ans = (cost_per_item * qty) + processing_fee;
+    Ok(ans)
 }
 
 #[cfg(test)]

exercises/error_handling/errors3.rs

@@ -4,15 +4,13 @@
 // Why not? What should we do to fix it?
 // Execute `rustlings hint errors3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
 
 fn main() {
     let mut tokens = 100;
     let pretend_user_input = "8";
 
-    let cost = total_cost(pretend_user_input)?;
+    let cost = total_cost(pretend_user_input).unwrap();
 
     if cost > tokens {
         println!("You can't afford that many!");

exercises/error_handling/errors4.rs

@@ -1,8 +1,6 @@
 // errors4.rs
 // Execute `rustlings hint errors4` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 #[derive(PartialEq, Debug)]
 struct PositiveNonzeroInteger(u64);
 
@@ -15,7 +13,13 @@ enum CreationError {
 impl PositiveNonzeroInteger {
     fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
         // Hmm...? Why is this only returning an Ok value?
-        Ok(PositiveNonzeroInteger(value as u64))
+        if value < 0 {
+            Err(CreationError::Negative)
+        } else if value == 0 {
+            Err(CreationError::Zero)
+        } else {
+            Ok(PositiveNonzeroInteger(value as u64))
+        }
     }
 }
 

exercises/error_handling/errors5.rs

@@ -7,7 +7,7 @@
 // For now, think of the `Box<dyn ...>` type as an "I want anything that does ???" type, which, given
 // Rust's usual standards for runtime safety, should strike you as somewhat lenient!
 
-// In short, this particular use case for boxes is for when you want to own a value and you care only that it is a 
+// In short, this particular use case for boxes is for when you want to own a value and you care only that it is a
 // type which implements a particular trait. To do so, The Box is declared as of type Box<dyn Trait> where Trait is the trait
 // the compiler looks for on any value used in that context. For this exercise, that context is the potential errors
 // which can be returned in a Result.
@@ -16,14 +16,12 @@
 
 // Execute `rustlings hint errors5` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 use std::error;
 use std::fmt;
 use std::num::ParseIntError;
 
 // TODO: update the return type of `main()` to make this compile.
-fn main() -> Result<(), Box<dyn ???>> {
+fn main() -> Result<(), Box<dyn error::Error>> {
     let pretend_user_input = "42";
     let x: i64 = pretend_user_input.parse()?;
     println!("output={:?}", PositiveNonzeroInteger::new(x)?);
@@ -46,7 +44,7 @@ impl PositiveNonzeroInteger {
         match value {
             x if x < 0 => Err(CreationError::Negative),
             x if x == 0 => Err(CreationError::Zero),
-            x => Ok(PositiveNonzeroInteger(x as u64))
+            x => Ok(PositiveNonzeroInteger(x as u64)),
         }
     }
 }

exercises/error_handling/errors6.rs

@@ -8,33 +8,34 @@
 
 // Execute `rustlings hint errors6` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
 
 // This is a custom error type that we will be using in `parse_pos_nonzero()`.
 #[derive(PartialEq, Debug)]
 enum ParsePosNonzeroError {
     Creation(CreationError),
-    ParseInt(ParseIntError)
+    ParseInt(ParseIntError),
 }
 
 impl ParsePosNonzeroError {
     fn from_creation(err: CreationError) -> ParsePosNonzeroError {
         ParsePosNonzeroError::Creation(err)
     }
-    // TODO: add another error conversion function here.
-    // fn from_parseint...
+
+    fn from_parseint(err: ParseIntError) -> ParsePosNonzeroError {
+        ParsePosNonzeroError::ParseInt(err)
+    }
 }
 
-fn parse_pos_nonzero(s: &str)
-    -> Result<PositiveNonzeroInteger, ParsePosNonzeroError>
-{
+fn parse_pos_nonzero(s: &str) -> Result<PositiveNonzeroInteger, ParsePosNonzeroError> {
     // TODO: change this to return an appropriate error instead of panicking
     // when `parse()` returns an error.
-    let x: i64 = s.parse().unwrap();
-    PositiveNonzeroInteger::new(x)
-        .map_err(ParsePosNonzeroError::from_creation)
+    match s.parse() {
+        Ok(x) => PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation),
+        Err(err) => Err(ParsePosNonzeroError::from_parseint(err)),
+    }
+
+    // PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation)
 }
 
 // Don't change anything below this line.
@@ -53,7 +54,7 @@ impl PositiveNonzeroInteger {
         match value {
             x if x < 0 => Err(CreationError::Negative),
             x if x == 0 => Err(CreationError::Zero),
-            x => Ok(PositiveNonzeroInteger(x as u64))
+            x => Ok(PositiveNonzeroInteger(x as u64)),
         }
     }
 }

exercises/options/options3.rs

@@ -1,8 +1,7 @@
 // options3.rs
 // Execute `rustlings hint options3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
+#[derive(Clone)]
 struct Point {
     x: i32,
     y: i32,
@@ -11,7 +10,7 @@ struct Point {
 fn main() {
     let y: Option<Point> = Some(Point { x: 100, y: 200 });
 
-    match y {
+    match y.clone() {
         Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
         _ => println!("no match"),
     }