Assignment 8 Done

src/assignments/assignment08/church.rs

@@ -35,17 +35,28 @@ pub fn zero<T: 'static>() -> Church<T> {
 
 /// Implement a function to add 1 to a given Church numeral.
 pub fn succ<T: 'static>(n: Church<T>) -> Church<T> {
-    todo!()
+    Rc::new(move |f| {
+        let n = n.clone();
+        Rc::new(move |x| f(n(f.clone())(x)))
+    })
 }
 
 /// Implement a function to add two Church numerals.
 pub fn add<T: 'static>(n: Church<T>, m: Church<T>) -> Church<T> {
-    todo!()
+    Rc::new(move |f| {
+        let n = n.clone();
+        let m = m.clone();
+        Rc::new(move |x| m(f.clone())(n(f.clone())(x)))
+    })
 }
 
 /// Implement a function to multiply (mult) two Church numerals.
 pub fn mult<T: 'static>(n: Church<T>, m: Church<T>) -> Church<T> {
-    todo!()
+    Rc::new(move |f| {
+        let n = n.clone();
+        let m = m.clone();
+        Rc::new(move |x| m(n(f.clone()))(x))
+    })
 }
 
 /// Implement a function to raise one Church numeral to the power of another.
@@ -56,18 +67,35 @@ pub fn mult<T: 'static>(n: Church<T>, m: Church<T>) -> Church<T> {
 /// base). Note: This function should be implemented *WITHOUT* using the `to_usize` or any
 /// `pow`-like method.
 pub fn exp<T: 'static>(n: usize, m: usize) -> Church<T> {
-    // ACTION ITEM: Uncomment the following lines and replace `todo!()` with your code.
+    let n = from_usize(n);
-    // let n = from_usize(n);
+    let m = from_usize(m);
-    // let m = from_usize(m);
+    m(n)
-    todo!()
 }
 
 /// Implement a function to convert a Church numeral to a usize type.
 pub fn to_usize<T: 'static + Default>(n: Church<T>) -> usize {
-    todo!()
+    let result = Rc::new(RefCell::new(0));
+    {
+        let result = result.clone();
+        let _unused = n(Rc::new(move |x| {
+            *result.borrow_mut() += 1;
+            x
+        }))(T::default());
+    }
+    {
+        let result = *result.borrow();
+        result
+    }
 }
 
 /// Implement a function to convert a usize type to a Church numeral.
 pub fn from_usize<T: 'static>(n: usize) -> Church<T> {
-    todo!()
+    Rc::new(move |f| {
+        Rc::new(move |mut x| {
+            for _ in 0..n {
+                x = f(x)
+            }
+            x
+        })
+    })
 }

src/assignments/assignment08/small_exercises.rs

@@ -7,8 +7,12 @@
 ///
 /// Refer `test_repeat` in `assignment08_grade.rs` for detailed examples.
 pub fn repeat<T, F: FnMut(T) -> T>(n: usize, mut f: F) -> impl FnMut(T) -> T {
-    todo!();
+    move |mut x| {
-    f // This line has been added to prevent compile error. You can erase this line.
+        for i in 0..n {
+            x = f(x)
+        }
+        x
+    }
 }
 
 /// Funny Map
@@ -20,7 +24,13 @@ pub fn repeat<T, F: FnMut(T) -> T>(n: usize, mut f: F) -> impl FnMut(T) -> T {
 ///
 /// Refer `test_funny_map` in `assignment08_grade.rs` for detailed examples.
 pub fn funny_map<T, F: Fn(T) -> T>(f: F, vs: Vec<T>) -> Vec<T> {
-    todo!()
+    let mut result = vec![];
+
+    for element in vs {
+        result.push(repeat(result.len(), &f)(element));
+    }
+
+    result
 }
 
 /// Count Repeat
@@ -33,7 +43,20 @@ pub fn count_repeat<T, F: Fn(T) -> T>(f: F, x: T) -> usize
 where
     T: PartialEq + Copy,
 {
-    todo!()
+    let mut set = vec![x];
+    let mut x = x;
+
+    loop {
+        x = f(x);
+
+        if set.contains(&x) {
+            break;
+        } else {
+            set.push(x);
+        }
+    }
+
+    set.len()
 }
 
 /// Either `T1`, or `T2`.
@@ -64,6 +87,9 @@ impl<T1, T2> Either2<T1, T2> {
         F1: FnOnce(T1) -> U1,
         F2: FnOnce(T2) -> U2,
     {
-        todo!()
+        match self {
+            Self::Case1 { inner } => Either2::Case1 { inner: f1(inner) },
+            Self::Case2 { inner } => Either2::Case2 { inner: f2(inner) },
+        }
     }
 }