fixed iterator1 exercise by giving the compiler less clues

standard_library_types/iterator1.rs

@@ -1,9 +1,10 @@
 // 1. Complete the divide function
 // 2. Uncomment and complete the second part of the main function
 // For part 2 there is a minor hint around line 100 and a major hint around line 128
-// There is a minor side quest in the "print_result_with_list" function
+// There are some final comments for when you are done around line 150
 // Have fun :-)
 
+
 // In production code you would not derive Debug, but implement it manually to get a better error message.
 #[derive(Debug,PartialEq,Eq)]
 enum DivisionError {
@@ -19,27 +20,6 @@ struct NotDivisibleError {
 // This function calculates a/b if a is divisible by b.
 // Otherwise it returns a suitable error.
 fn divide(a: i32, b: i32) -> Result<i32,DivisionError> {
-    if b == 0 {
-
-    }
-    match a % b {
-
-    }
-}
-
-// these print functions exist, so you have to satisfy their input types in the main function
-fn print_list_of_results(l: Vec<Result<i32,DivisionError>>) {
-    println!("{:?}", l);
-}
-fn print_result_with_list(r: Result<Vec<i32>,DivisionError>) {
-    // side quest: why is there no semicolon in this function?
-    match r {
-        Ok(v) => println!("All numbers were successfully divided: {:?}", v),
-        Err(e) => match e {
-            DivisionError::NotDivisible(nde) => println!("Failed to divide {} by {}: Not divisible!", nde.divident, nde.divisor),
-            DivisionError::DivideByZero => println!("Can't divide by zero"),
-        },
-    };
 }
 
 #[allow(dead_code)]
@@ -54,23 +34,28 @@ fn main() {
     assert_eq!(divide(81,9),Ok(9));
     assert_eq!(divide(81,6),Err(DivisionError::NotDivisible(NotDivisibleError{divident:81,divisor:6})));
     assert_eq!(divide(81,0),Err(DivisionError::DivideByZero));
+    assert_eq!(divide(0,81),Ok(0));
     println!("Your divide function seems to work! Good Job.");
     
     /* Second part of main. Uncomment to continue.
+    // Don't change these numbers. It will break the assertions later in the code.
     let numbers = vec![27,297,38502,81];
     
     let division_results = // Do not convert the results into a Vec yet. Leave them iterable for now.
     let operation_mode = OperationMode::ResultWithList;
     match operation_mode {
         OperationMode::ResultWithList => {
-            
-            print_result_with_list(x);
+
+            println!("{:?}", x);
+            assert_eq!(format!("{:?}",x), "Ok([1, 11, 1426, 3])");
         },
         OperationMode::ListOfResults => {
-            
-            print_list_of_results(x);
+
+            println!("{:?}", x);
+            assert_eq!(format!("{:?}",x), "[Ok(1), Ok(11), Ok(1426), Ok(3)]");
         },
-    } */
+    }
+    */
 }
 
 
@@ -90,6 +75,20 @@ fn main() {
 
 
 
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@@ -126,3 +125,40 @@ fn main() {
 
 
 // Major hint: Have a look at the Iter trait and at the explanation of its collect function. Especially the part about Result is interesting.
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+// Final comments
+// When you call the function `print_result_with_list` with x, you don't need any type annotations on x anymore.
+// The compiler can infer its type through the function's input type.
+
+#[allow(dead_code)]
+// Don't use this function to solve the exercise
+fn print_result_with_list(r: Result<Vec<i32>,DivisionError>) {
+    // side quest: why is there no semicolon in this function?
+    match r {
+        Ok(v) => println!("All numbers were successfully divided: {:?}", v),
+        Err(e) => match e {
+            DivisionError::NotDivisible(nde) => println!("Failed to divide {} by {}: Not divisible!", nde.divident, nde.divisor),
+            DivisionError::DivideByZero => println!("Can't divide by zero"),
+        },
+    };
+}

standard_library_types/iterator1_solution.rs

@@ -23,10 +23,13 @@ fn divide(a: i32, b: i32) -> Result<i32,DivisionError> {
     }
 }
 
-// these print functions exist, so you have to satisfy their input types in the main function
-fn print_list_of_results(l: Vec<Result<i32,DivisionError>>) {
-    println!("{:?}", l);
+#[allow(dead_code)]
+enum OperationMode {
+    ListOfResults,
+    ResultWithList,
 }
+
+#[allow(dead_code)]
 fn print_result_with_list(r: Result<Vec<i32>,DivisionError>) {
     // side quest: why is there no semicolon in this function?
     match r {
@@ -38,12 +41,6 @@ fn print_result_with_list(r: Result<Vec<i32>,DivisionError>) {
     };
 }
 
-#[allow(dead_code)]
-enum OperationMode {
-    ListOfResults,
-    ResultWithList,
-}
-
 fn main() {
     // These asserts check that your `divide` function works.
     // In production code these would be tests
@@ -51,6 +48,7 @@ fn main() {
     assert_eq!(divide(81,6),Err(DivisionError::NotDivisible(NotDivisibleError{divident:81,divisor:6})));
     assert_eq!(divide(81,0),Err(DivisionError::DivideByZero));
     println!("Your divide function seems to work! Good Job.");
+    // Don't change these numbers. It will break the assertions later in the code.
     let numbers = vec![27,297,38502,81];
     let numbers_iterator = numbers.into_iter();
     let division_results = numbers_iterator.map(|n| divide(n, 27));
@@ -58,11 +56,13 @@ fn main() {
     match operation_mode {
         OperationMode::ResultWithList => {
             let x : Result<Vec<_>,_> = division_results.collect();
-            print_result_with_list(x);
+            //print_result_with_list(x);
+            assert_eq!(format!("{:?}",x), "Ok([1, 11, 1426, 3])");
         },
         OperationMode::ListOfResults => {
             let x : Vec<_> = division_results.collect();
-            print_list_of_results(x);
+            println!("{:?}", x);
+            assert_eq!(format!("{:?}",x), "[Ok(1), Ok(11), Ok(1426), Ok(3)]");
         },
     }
 }