errors3 solution

exercises/13_error_handling/errors3.rs

@@ -4,6 +4,17 @@
 
 use std::num::ParseIntError;
 
+// Don't change this function.
+fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
+    let processing_fee = 1;
+    let cost_per_item = 5;
+    let qty = item_quantity.parse::<i32>()?;
+
+    Ok(qty * cost_per_item + processing_fee)
+}
+
+// TODO: Fix the compiler error by changing the signature and body of the
+// `main` function.
 fn main() {
     let mut tokens = 100;
     let pretend_user_input = "8";
@@ -14,14 +25,6 @@ fn main() {
         println!("You can't afford that many!");
     } else {
         tokens -= cost;
-        println!("You now have {} tokens.", tokens);
+        println!("You now have {tokens} tokens.");
     }
 }
-
-fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
-    let processing_fee = 1;
-    let cost_per_item = 5;
-    let qty = item_quantity.parse::<i32>()?;
-
-    Ok(qty * cost_per_item + processing_fee)
-}

rustlings-macros/info.toml

@@ -675,8 +675,8 @@ If other functions can return a `Result`, why shouldn't `main`? It's a fairly
 common convention to return something like `Result<(), ErrorType>` from your
 `main` function.
 
-The unit (`()`) type is there because nothing is really needed in terms of
-positive results."""
+The unit type `()` is there because nothing is really needed in terms of a
+positive result."""
 
 [[exercises]]
 name = "errors4"

solutions/13_error_handling/errors3.rs

@@ -1 +1,32 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// This is a program that is trying to use a completed version of the
+// `total_cost` function from the previous exercise. It's not working though!
+// Why not? What should we do to fix it?
+
+use std::num::ParseIntError;
+
+// Don't change this function.
+fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
+    let processing_fee = 1;
+    let cost_per_item = 5;
+    let qty = item_quantity.parse::<i32>()?;
+
+    Ok(qty * cost_per_item + processing_fee)
+}
+
+fn main() -> Result<(), ParseIntError> {
+    //    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ added
+    let mut tokens = 100;
+    let pretend_user_input = "8";
+
+    let cost = total_cost(pretend_user_input)?;
+
+    if cost > tokens {
+        println!("You can't afford that many!");
+    } else {
+        tokens -= cost;
+        println!("You now have {tokens} tokens.");
+    }
+
+    // Added this line to return the `Ok` variant of the expected `Result`.
+    Ok(())
+}