iterators3 solution

exercises/18_iterators/iterators3.rs

@@ -1,40 +1,26 @@
-// This is a bigger exercise than most of the others! You can do it! Here is
-// your mission, should you choose to accept it:
-// 1. Complete the divide function to get the first four tests to pass.
-// 2. Get the remaining tests to pass by completing the result_with_list and
-//    list_of_results functions.
-
 #[derive(Debug, PartialEq, Eq)]
 enum DivisionError {
-    NotDivisible(NotDivisibleError),
     DivideByZero,
+    NotDivisible,
 }
 
-#[derive(Debug, PartialEq, Eq)]
+// TODO: Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
-struct NotDivisibleError {
-    dividend: i32,
-    divisor: i32,
-}
-
-// Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
 // Otherwise, return a suitable error.
 fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
     todo!();
 }
 
-// Complete the function and return a value of the correct type so the test
+// TODO: Add the correct return type and complete the function body.
-// passes.
+// Desired output: `Ok([1, 11, 1426, 3])`
-// Desired output: Ok([1, 11, 1426, 3])
+fn result_with_list() {
-fn result_with_list() -> () {
+    let numbers = [27, 297, 38502, 81];
-    let numbers = vec![27, 297, 38502, 81];
     let division_results = numbers.into_iter().map(|n| divide(n, 27));
 }
 
-// Complete the function and return a value of the correct type so the test
+// TODO: Add the correct return type and complete the function body.
-// passes.
+// Desired output: `[Ok(1), Ok(11), Ok(1426), Ok(3)]`
-// Desired output: [Ok(1), Ok(11), Ok(1426), Ok(3)]
+fn list_of_results() {
-fn list_of_results() -> () {
+    let numbers = [27, 297, 38502, 81];
-    let numbers = vec![27, 297, 38502, 81];
     let division_results = numbers.into_iter().map(|n| divide(n, 27));
 }
 
@@ -52,19 +38,13 @@ mod tests {
     }
 
     #[test]
-    fn test_not_divisible() {
+    fn test_divide_by_0() {
-        assert_eq!(
+        assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
-            divide(81, 6),
-            Err(DivisionError::NotDivisible(NotDivisibleError {
-                dividend: 81,
-                divisor: 6
-            }))
-        );
     }
 
     #[test]
-    fn test_divide_by_0() {
+    fn test_not_divisible() {
-        assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
+        assert_eq!(divide(81, 6), Err(DivisionError::NotDivisible));
     }
 
     #[test]
@@ -74,14 +54,11 @@ mod tests {
 
     #[test]
     fn test_result_with_list() {
-        assert_eq!(format!("{:?}", result_with_list()), "Ok([1, 11, 1426, 3])");
+        assert_eq!(result_with_list().unwarp(), [1, 11, 1426, 3]);
     }
 
     #[test]
     fn test_list_of_results() {
-        assert_eq!(
+        assert_eq!(list_of_results(), [Ok(1), Ok(11), Ok(1426), Ok(3)]);
-            format!("{:?}", list_of_results()),
-            "[Ok(1), Ok(11), Ok(1426), Ok(3)]"
-        );
     }
 }

rustlings-macros/info.toml

@@ -922,8 +922,8 @@ powerful and very general. Rust just needs to know the desired type."""
 name = "iterators3"
 dir = "18_iterators"
 hint = """
-The `divide` function needs to return the correct error when even division is
+The `divide` function needs to return the correct error when the divisor is 0 or
-not possible.
+when even division is not possible.
 
 The `division_results` variable needs to be collected into a collection type.
 
@@ -934,7 +934,7 @@ The `list_of_results` function needs to return a vector of results.
 
 See https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.collect for
 how the `FromIterator` trait is used in `collect()`. This trait is REALLY
-powerful! It can make the solution to this exercise infinitely easier."""
+powerful! It can make the solution to this exercise much easier."""
 
 [[exercises]]
 name = "iterators4"

solutions/18_iterators/iterators3.rs

@@ -1 +1,73 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+#[derive(Debug, PartialEq, Eq)]
+enum DivisionError {
+    DivideByZero,
+    NotDivisible,
+}
+
+fn divide(a: i64, b: i64) -> Result<i64, DivisionError> {
+    if b == 0 {
+        return Err(DivisionError::DivideByZero);
+    }
+
+    if a % b != 0 {
+        return Err(DivisionError::NotDivisible);
+    }
+
+    Ok(a / b)
+}
+
+fn result_with_list() -> Result<Vec<i64>, DivisionError> {
+    //                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    let numbers = [27, 297, 38502, 81];
+    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+    // Collects to the expected return type. Returns the first error in the
+    // division results (if one exists).
+    division_results.collect()
+}
+
+fn list_of_results() -> Vec<Result<i64, DivisionError>> {
+    //               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    let numbers = [27, 297, 38502, 81];
+    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+    // Collects to the expected return type.
+    division_results.collect()
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_success() {
+        assert_eq!(divide(81, 9), Ok(9));
+    }
+
+    #[test]
+    fn test_divide_by_0() {
+        assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
+    }
+
+    #[test]
+    fn test_not_divisible() {
+        assert_eq!(divide(81, 6), Err(DivisionError::NotDivisible));
+    }
+
+    #[test]
+    fn test_divide_0_by_something() {
+        assert_eq!(divide(0, 81), Ok(0));
+    }
+
+    #[test]
+    fn test_result_with_list() {
+        assert_eq!(result_with_list().unwrap(), [1, 11, 1426, 3]);
+    }
+
+    #[test]
+    fn test_list_of_results() {
+        assert_eq!(list_of_results(), [Ok(1), Ok(11), Ok(1426), Ok(3)]);
+    }
+}