From 3e8508dd04c20584999cc7de0c2012f2ade589dc Mon Sep 17 00:00:00 2001
From: Enrico Bozzolini <boz@ti8m.ch>
Date: Thu, 4 Jun 2020 21:48:23 +0200
Subject: [PATCH] Solve box and iterators

---
 exercises/standard_library_types/box1.rs       |  8 +++-----
 exercises/standard_library_types/iterators3.rs | 12 +++++++++---
 exercises/standard_library_types/iterators4.rs | 11 +++++++++--
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/exercises/standard_library_types/box1.rs b/exercises/standard_library_types/box1.rs
index 2248962e..70b98e40 100644
--- a/exercises/standard_library_types/box1.rs
+++ b/exercises/standard_library_types/box1.rs
@@ -16,11 +16,9 @@
 //
 // Execute `rustlings hint box1` for hints :)
 
-// I AM NOT DONE
-
 #[derive(PartialEq, Debug)]
 pub enum List {
-    Cons(i32, List),
+    Cons(i32, Box<List>),
     Nil,
 }
 
@@ -30,11 +28,11 @@ fn main() {
 }
 
 pub fn create_empty_list() -> List {
-    unimplemented!()
+    List::Nil
 }
 
 pub fn create_non_empty_list() -> List {
-    unimplemented!()
+    List::Cons(1, Box::new(List::Nil))
 }
 
 #[cfg(test)]
diff --git a/exercises/standard_library_types/iterators3.rs b/exercises/standard_library_types/iterators3.rs
index 353cea62..d2b5387c 100644
--- a/exercises/standard_library_types/iterators3.rs
+++ b/exercises/standard_library_types/iterators3.rs
@@ -7,8 +7,6 @@
 // Execute `rustlings hint iterators3` to get some hints!
 // Have fun :-)
 
-// I AM NOT DONE
-
 #[derive(Debug, PartialEq, Eq)]
 pub enum DivisionError {
     NotDivisible(NotDivisibleError),
@@ -24,7 +22,15 @@ pub struct NotDivisibleError {
 // This function should calculate `a` divided by `b` if `a` is
 // evenly divisible by b.
 // Otherwise, it should return a suitable error.
-pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {}
+pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
+    if b == 0 {
+        Err(DivisionError::DivideByZero)
+    } else if a % b != 0 {
+        Err(DivisionError::NotDivisible(NotDivisibleError{dividend: a, divisor: b}))
+    } else {
+        Ok(a / b)
+    }
+}
 
 #[cfg(test)]
 mod tests {
diff --git a/exercises/standard_library_types/iterators4.rs b/exercises/standard_library_types/iterators4.rs
index 88862838..e1e4de5b 100644
--- a/exercises/standard_library_types/iterators4.rs
+++ b/exercises/standard_library_types/iterators4.rs
@@ -1,7 +1,5 @@
 // iterators4.rs
 
-// I AM NOT DONE
-
 pub fn factorial(num: u64) -> u64 {
     // Complete this function to return the factorial of num
     // Do not use:
@@ -12,6 +10,15 @@ pub fn factorial(num: u64) -> u64 {
     // For an extra challenge, don't use:
     // - recursion
     // Execute `rustlings hint iterators4` for hints.
+
+    // Recusive
+    // match num {
+    //     0 | 1 => 1,
+    //     num   => num * factorial(num - 1),
+    // }
+
+    // Functional
+    (1..num+1).product()
 }
 
 #[cfg(test)]