errors3 solution

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(())
+}