assignment 1~5: fixes

- assignment05/pascal.mlw: lowered the difficulty (one more invariant given)
- assignment02, 03: minor fixes & divide into sub-problems

assets/why3/assignment05/max.mlw

@@ -4,7 +4,6 @@
   return the maximum element of the array.
   
   You should stengthen the loop invariant.
-  
 *)
 
 module Max
@@ -20,8 +19,9 @@ module Max
     ensures { exists i. 0 <= i < n -> a[i] = max }
   = let ref max = 0 in
     for i = 0 to n - 1 do
-      (* IMPORTANT: MODIFY ONLY THIS INVARIANT, OR YOU'LL GET ZERO POINTS *)
+      (* IMPORTANT: DON'T MODIFY THE ABOVE LINES *)
-      invariant { true (*TODO*) }
+      invariant { true (* TODO: Replace `true` with your solution *) }
+      (* IMPORTANT: DON'T MODIFY THE BELOW LINES *)
       if max < a[i] then max <- a[i];
     done;
     max

assets/why3/assignment05/pascal.mlw

@@ -1,10 +1,14 @@
+(* Pascal
+
+  Prove that the Pascal's triangle indeed computes combinations.
+  HINT: https://en.wikipedia.org/wiki/Pascal%27s_triangle
+*)
+
 module Pascal
   use int.Int
   use ref.Ref
   use array.Array
 
-  (* HINT: https://en.wikipedia.org/wiki/Pascal%27s_triangle *)
-  (* You should understand the Pascal's triangle first to find good invariants *) 
   let rec function comb (n k: int) : int
     requires { 0 <= k <= n }
     variant  { n }
@@ -12,6 +16,7 @@ module Pascal
   = if k = 0 || k = n then 1 else comb (n-1) k + comb (n-1) (k-1)
 
   (* Insert appropriate invariants so that Why3 can verify this function. *)
+  (* You SHOULD understand the Pascal's triangle first to find good invariants. *) 
   let chooses (n : int) : array int
     requires { n > 0 }
     ensures  { forall i: int.
@@ -20,10 +25,12 @@ module Pascal
     let ref row = Array.make 1 1 in
     for r = 1 to n do
       invariant { length row = r }
-      invariant { true (*TODO*) }
+      invariant { forall c: int. 0 <= c < r -> row[c] = comb (r-1) c } 
       let new_row = Array.make (r+1) 1 in
       for c = 1 to r-1 do
-        invariant { true (*TODO*) }
+        (* IMPORTANT: DON'T MODIFY THE ABOVE LINES *)
+        invariant { true (* TODO: Replace `true` with your solution *) }
+        (* IMPORTANT: DON'T MODIFY THE BELOW LINES *)
         new_row[c] <- row[c-1] + row[c]
       done;
       row <- new_row

assets/why3/exercises/ex1_eucl_div.mlw

@@ -11,7 +11,6 @@ module Division
 
   use int.Int
 
-  (* IMPORTANT: DON'T MODIFY LINES EXCEPT `TODO`s OR YOU WILL GET ZERO POINTS *)
   let division (a b: int) : int
     requires { a >= 0 }
     requires { b > 0 }
@@ -20,7 +19,7 @@ module Division
     let ref q = 0 in
     let ref r = a in
     while r >= b do
-      invariant { true (*TODO*) } 
+      invariant { true (* TODO: Replace `true` with your solution *) } 
       variant { r }
       q <- q + 1;
       r <- r - b

assets/why3/exercises/ex2_fact.mlw

@@ -39,10 +39,8 @@ module FactLoop
   = let ref m = 0 in
     let ref r = 1 in
     while m < n do
-      (* IMPORTANT: DON'T MODIFY THE ABOVE LINES *) 
+      invariant { true (* TODO: Replace `true` with your solution  *) }
-      invariant { true (* TODO *) }
+      variant { n (* TODO: Replace `n` with your solution  *) }
-      variant { n (* TODO *) }
-      (* IMPORTANT: DON'T MODIFY THE BELOW LINES *) 
       m <- m + 1;
       r <- r * m
     done;

assets/why3/exercises/ex3_two_way.mlw

@@ -31,13 +31,11 @@ module TwoWaySort
     let ref j = length a - 1 in
     while i < j do
       invariant { 0 <= i /\ j < length a }
-      (* IMPORTANT: DON'T MODIFY THE ABOVE LINES *)
       invariant { forall i1: int. 0 <= i1 < i 
-        -> true (* TODO *) }
+        -> true (* TODO: Replace `true` with your solution *) }
       invariant { forall i2: int. j < i2 < length a 
-        -> true (* TODO *) }
+        -> true (* TODO: Replace `true` with your solution *) }
-      invariant { true (* TODO *) }
+      invariant { true (* TODO: Replace `true` with your solution *) }
-      (* IMPORTANT: DON'T MODIFY THE BELOW LINES *)
       variant { j - i }
       if not a[i] then
         incr i

assets/why3/exercises/solutions/ex1_eucl_div_sol.mlw

@@ -0,0 +1,30 @@
+(* Euclidean division
+
+   1. Prove correctness of euclideian divison:
+     `division a b` returns an integer `q` such that
+      `a = bq+r` and `0 <= r < b` for some `r`.
+   
+     - You have to strengthen the precondition.
+     - You have to strengthen the loop invariant.
+*)
+
+module Division
+
+  use int.Int
+
+  let division (a b: int) : int
+    requires { a >= 0 }
+    requires { b > 0 }
+    ensures  { exists r: int. a = b * result + r /\ 0 <= r < b }
+  =
+    let ref q = 0 in
+    let ref r = a in
+    while r >= b do
+      invariant { a = b * q + r /\ 0 <= r } 
+      variant { r }
+      q <- q + 1;
+      r <- r - b
+    done;
+    q
+
+end

assets/why3/exercises/solutions/ex2_fact_sol.mlw

@@ -0,0 +1,37 @@
+(* Two programs to compute the factorial
+     
+*)
+
+module FactRecursive
+
+  use int.Int
+  use int.Fact
+
+  let rec fact_rec (n: int) : int
+    requires { n >= 0 }
+    ensures  { result = fact n }
+    variant { n }
+  =
+    if n = 0 then 1 else n * fact_rec (n - 1)
+
+end
+
+module FactLoop
+
+  use int.Int
+  use int.Fact
+
+  let fact_loop (n: int) : int
+    requires { 0 < n }
+    ensures  { result = fact n }
+  = let ref m = 0 in
+    let ref r = 1 in
+    while m < n do
+      invariant { 0 <= m <= n /\ r = fact m }
+      variant { n - m }
+      m <- m + 1;
+      r <- r * m
+    done;
+    r
+
+end

assets/why3/exercises/solutions/ex3_two_way_sol.mlw

@@ -0,0 +1,49 @@
+(* Two Way Sort
+
+   The following program sorts an array of Boolean values, with False<True.
+   
+   E.g.
+     two_way_sorted [True; False; False; True; False]
+     = [False; False; False; True; True]
+
+   - Strengthen the invariant to prove correctness.
+*)
+
+module TwoWaySort
+
+  use int.Int
+  use bool.Bool
+  use ref.Refint
+  use array.Array
+  use array.ArraySwap
+  use array.ArrayPermut
+
+  predicate (<<) (x y: bool) = x = False \/ y = True
+
+  predicate sorted (a: array bool) =
+    forall i1 i2: int. 0 <= i1 <= i2 < a.length -> a[i1] << a[i2]
+
+  let two_way_sort (a: array bool) : unit
+    ensures { sorted a }
+    ensures { permut_all (old a) a }
+  =
+    let ref i = 0 in
+    let ref j = length a - 1 in
+    while i < j do
+      invariant { 0 <= i /\ j < length a }
+      invariant { forall i1: int. 0 <= i1 < i -> a[i1] = False }
+      invariant { forall i2: int. j < i2 < length a -> a[i2] = True }
+      invariant { permut_all (old a) a }
+      variant { j - i }
+      if not a[i] then
+        incr i
+      else if a[j] then
+        decr j
+      else begin
+        swap a i j;
+        incr i;
+        decr j
+      end
+    done
+
+end

scripts/grade-02.sh

@@ -24,7 +24,7 @@ run_linters || exit 1
 for RUNNER in "${RUNNERS[@]}"; do
     echo "Running with $RUNNER..."
 
-    TESTS=("--lib assignment02_grade")
+    TESTS=("--lib assignment02")
     if [ $(run_tests) -ne 0 ]; then
         exit 1
     fi

scripts/grade-03.sh

@@ -24,7 +24,7 @@ run_linters || exit 1
 for RUNNER in "${RUNNERS[@]}"; do
     echo "Running with $RUNNER..."
 
-    TESTS=("--lib assignment03_grade")
+    TESTS=("--lib assignment03")
     if [ $(run_tests) -ne 0 ]; then
         exit 1
     fi

src/assignments/assignment02.rs

@@ -1,176 +0,0 @@
-//! Assignment 2: Mastering common programming concepts (1/2).
-//!
-//! The primary goal of this assignment is to re-learn the common programming concepts in Rust, especially those in the Rust Book chapters 3 and 5.
-//! Please make sure you're comfortable with the concepts to proceed on to the next assignments.
-//!
-//! You should fill out the `todo!()` placeholders in such a way that `/scripts/grade-02.sh` works fine.
-//! See `assignment02_grade.rs` and `/scripts/grade-02.sh` for the test script.
-
-use std::ops::Mul;
-
-const FAHRENHEIT_OFFSET: f64 = 32.0;
-const FAHRENHEIT_SCALE: f64 = 5.0 / 9.0;
-
-/// Converts Fahrenheit to Celsius temperature degree.
-pub fn fahrenheit_to_celsius(degree: f64) -> f64 {
-    todo!()
-}
-
-/// Capitalizes English alphabets (leaving the other characters intact).
-pub fn capitalize(input: String) -> String {
-    todo!()
-}
-
-/// Returns the sum of the given array. (We assume the absence of integer overflow.)
-pub fn sum_array(input: &[u64]) -> u64 {
-    todo!()
-}
-
-/// Given a non-negative integer, say `n`, return the smallest integer of the form `3^m` that's greater than or equal to `n`.
-///
-/// For instance, up3(6) = 9, up3(9) = 9, up3(10) = 27. (We assume the absence of integer overflow.)
-pub fn up3(n: u64) -> u64 {
-    todo!()
-}
-
-/// Returns the greatest common divisor (GCD) of two non-negative integers. (We assume the absence of integer overflow.)
-pub fn gcd(lhs: u64, rhs: u64) -> u64 {
-    todo!()
-}
-
-/// Returns the array of nC0, nC1, nC2, ..., nCn, where nCk = n! / (k! * (n-k)!). (We assume the absence of integer overflow.)
-///
-/// Consult <https://en.wikipedia.org/wiki/Pascal%27s_triangle> for computation of binomial coefficients without integer overflow.
-pub fn chooses(n: u64) -> Vec<u64> {
-    todo!()
-}
-
-/// Returns the "zip" of two vectors.
-///
-/// For instance, `zip(vec![1, 2, 3], vec![4, 5])` equals to `vec![(1, 4), (2, 5)]`.
-/// Here, `3` is ignored because it doesn't have a partner.
-pub fn zip(lhs: Vec<u64>, rhs: Vec<u64>) -> Vec<(u64, u64)> {
-    todo!()
-}
-
-/// 2x2 matrix of the following configuration:
-///
-/// a, b
-/// c, d
-#[derive(Debug, Clone, Copy)]
-struct Mat2 {
-    a: u64,
-    b: u64,
-    c: u64,
-    d: u64,
-}
-
-/// 2x1 matrix of the following configuration:
-///
-/// a
-/// b
-#[derive(Debug, Clone, Copy)]
-struct Vec2 {
-    a: u64,
-    b: u64,
-}
-
-impl Mat2 {
-    /// Creates an identity matrix.
-    fn new() -> Self {
-        Self {
-            a: 1,
-            b: 0,
-            c: 0,
-            d: 1,
-        }
-    }
-}
-
-impl Mul<Mat2> for Mat2 {
-    type Output = Mat2;
-
-    fn mul(self, rhs: Mat2) -> Self::Output {
-        todo!()
-    }
-}
-
-impl Mul<Vec2> for Mat2 {
-    type Output = Vec2;
-
-    fn mul(self, rhs: Vec2) -> Self::Output {
-        todo!()
-    }
-}
-
-impl Mat2 {
-    /// Calculates the power of matrix.
-    fn power(self, power: u64) -> Mat2 {
-        todo!()
-    }
-}
-
-impl Vec2 {
-    /// Gets the upper value of vector.
-    fn get_upper(self) -> u64 {
-        todo!()
-    }
-}
-
-/// The matrix used for calculating Fibonacci numbers.
-const FIBONACCI_MAT: Mat2 = Mat2 {
-    a: 1,
-    b: 1,
-    c: 1,
-    d: 0,
-};
-
-/// The vector used for calculating Fibonacci numbers.
-const FIBONACCI_VEC: Vec2 = Vec2 { a: 1, b: 0 };
-
-/// Calculates the Fibonacci number. (We assume the absence of integer overflow.)
-///
-/// Consult <https://web.media.mit.edu/~holbrow/post/calculating-fibonacci-numbers-with-matrices-and-linear-algebra/> for matrix computation of Fibonacci numbers.
-pub fn fibonacci(n: u64) -> u64 {
-    (FIBONACCI_MAT.power(n) * FIBONACCI_VEC).get_upper()
-}
-
-/// 2x2 floating-point matrix of the following configuration:
-///
-/// a, b
-/// c, d
-#[derive(Debug, Clone, Copy)]
-pub struct FMat2 {
-    /// row 1, column 1
-    pub a: f64,
-    /// row 1, column 2
-    pub b: f64,
-    /// row 2, column 1
-    pub c: f64,
-    /// row 2, column 2
-    pub d: f64,
-}
-
-impl FMat2 {
-    /// Returns the inverse of the given matrix. (We assume the given matrix is always invertible.)
-    /// Hint: https://www.cuemath.com/algebra/inverse-of-2x2-matrix/
-    ///
-    /// # Example
-    ///
-    /// ```
-    /// assert_eq!(
-    ///     Mat2 { a: 1.0, b: 1.0, c: 2.0, d: 3.0 }.inverse(),
-    ///     Mat2 { a: 3.0, b: -1.0, c: -2.0, d: 1.0}
-    /// );
-    /// ```
-    pub fn inverse(self) -> Self {
-        todo!()
-    }
-}
-
-/// Writes down the lyrics of "twelve days of christmas".
-///
-/// Hint: Google the song title for lyrics and look at the test code for the expected result.
-pub fn twelve_days_of_christmas_lyrics() -> String {
-    todo!()
-}

src/assignments/assignment02/mod.rs

@@ -0,0 +1,13 @@
+//! Assignment 2: Mastering common programming concepts (1/2).
+//!
+//! The primary goal of this assignment is to re-learn the common programming concepts in Rust, especially those in the Rust Book chapters 3 and 5.
+//! Please make sure you're comfortable with the concepts to proceed on to the next assignments.
+//!
+//! You should fill out the `todo!()` placeholders in such a way that `/scripts/grade-02.sh` works fine.
+//! See `*_grade.rs` and `/scripts/grade-02.sh` for the test script.
+
+pub mod small_problems;
+mod small_problems_grade;
+
+pub mod vec_and_mat;
+mod vec_and_mat_grade;

src/assignments/assignment02/small_problems.rs

@@ -0,0 +1,46 @@
+//! Small problems.
+
+const FAHRENHEIT_OFFSET: f64 = 32.0;
+const FAHRENHEIT_SCALE: f64 = 5.0 / 9.0;
+
+/// Converts Fahrenheit to Celsius temperature degree.
+pub fn fahrenheit_to_celsius(degree: f64) -> f64 {
+    todo!()
+}
+
+/// Capitalizes English alphabets (leaving the other characters intact).
+pub fn capitalize(input: String) -> String {
+    todo!()
+}
+
+/// Returns the sum of the given array. (We assume the absence of integer overflow.)
+pub fn sum_array(input: &[u64]) -> u64 {
+    todo!()
+}
+
+/// Given a non-negative integer, say `n`, return the smallest integer of the form `3^m` that's greater than or equal to `n`.
+///
+/// For instance, up3(6) = 9, up3(9) = 9, up3(10) = 27. (We assume the absence of integer overflow.)
+pub fn up3(n: u64) -> u64 {
+    todo!()
+}
+
+/// Returns the greatest common divisor (GCD) of two non-negative integers. (We assume the absence of integer overflow.)
+pub fn gcd(lhs: u64, rhs: u64) -> u64 {
+    todo!()
+}
+
+/// Returns the array of nC0, nC1, nC2, ..., nCn, where nCk = n! / (k! * (n-k)!). (We assume the absence of integer overflow.)
+///
+/// Consult <https://en.wikipedia.org/wiki/Pascal%27s_triangle> for computation of binomial coefficients without integer overflow.
+pub fn chooses(n: u64) -> Vec<u64> {
+    todo!()
+}
+
+/// Returns the "zip" of two vectors.
+///
+/// For instance, `zip(vec![1, 2, 3], vec![4, 5])` equals to `vec![(1, 4), (2, 5)]`.
+/// Here, `3` is ignored because it doesn't have a partner.
+pub fn zip(lhs: Vec<u64>, rhs: Vec<u64>) -> Vec<(u64, u64)> {
+    todo!()
+}

src/assignments/assignment02/small_problems_grade.rs

@@ -0,0 +1,137 @@
+#[cfg(test)]
+mod test {
+    use crate::assignments::assignment02::small_problems::*;
+
+    #[test]
+    fn test_fahrenheit() {
+        assert_eq!(fahrenheit_to_celsius(32.0), 0.0);
+        assert_eq!(fahrenheit_to_celsius(212.0), 100.0);
+    }
+
+    #[test]
+    fn test_capitalize() {
+        assert_eq!(
+            capitalize(String::from("aAbbBcccCddddD❤한글과✓")),
+            String::from("AABBBCCCCDDDDD❤한글과✓"),
+        );
+        assert_eq!(capitalize(String::from("Tschüß")), String::from("TSCHüß"));
+    }
+
+    #[test]
+    fn test_up3() {
+        assert_eq!(up3(0), 1);
+        assert_eq!(up3(1), 1);
+        assert_eq!(up3(6), 9);
+        assert_eq!(up3(9), 9);
+        assert_eq!(up3(10), 27);
+        assert_eq!(up3(1_000_000), 1_594_323);
+        assert_eq!(up3(3u64.pow(39).wrapping_add(1)), 3u64.pow(40));
+        assert_eq!(up3(3u64.pow(40)), 3u64.pow(40));
+    }
+
+    #[test]
+    fn test_gcd() {
+        assert_eq!(gcd(5, 1), 1);
+        assert_eq!(gcd(3, 3), 3);
+        assert_eq!(gcd(2, 6), 2);
+        assert_eq!(gcd(24, 18), 6);
+        assert_eq!(gcd(20, 63), 1);
+        assert_eq!(gcd(0, 33), 33);
+    }
+
+    #[test]
+    fn test_sum_array() {
+        assert_eq!(sum_array(&[]), 0);
+        assert_eq!(sum_array(&[1]), 1);
+        assert_eq!(sum_array(&[1, 2, 3, 4, 5, 100]), 115);
+    }
+
+    #[test]
+    fn test_chooses() {
+        assert_eq!(chooses(0), vec![1]);
+        assert_eq!(chooses(1), vec![1, 1]);
+        assert_eq!(chooses(5), vec![1, 5, 10, 10, 5, 1]);
+        assert_eq!(chooses(6), vec![1, 6, 15, 20, 15, 6, 1]);
+        assert_eq!(
+            chooses(67),
+            vec![
+                1,
+                67,
+                2211,
+                47905,
+                766480,
+                9657648,
+                99795696,
+                869648208,
+                6522361560,
+                42757703560,
+                247994680648,
+                1285063345176,
+                5996962277488,
+                25371763481680,
+                97862516286480,
+                345780890878896,
+                1123787895356412,
+                3371363686069236,
+                9364899127970100,
+                24151581961607100,
+                57963796707857040,
+                129728497393775280,
+                271250494550621040,
+                530707489338171600,
+                972963730453314600,
+                1673497616379701112,
+                2703342303382594104,
+                4105075349580976232,
+                5864393356544251760,
+                7886597962249166160,
+                9989690752182277136,
+                11923179284862717872,
+                13413576695470557606,
+                14226520737620288370,
+                14226520737620288370,
+                13413576695470557606,
+                11923179284862717872,
+                9989690752182277136,
+                7886597962249166160,
+                5864393356544251760,
+                4105075349580976232,
+                2703342303382594104,
+                1673497616379701112,
+                972963730453314600,
+                530707489338171600,
+                271250494550621040,
+                129728497393775280,
+                57963796707857040,
+                24151581961607100,
+                9364899127970100,
+                3371363686069236,
+                1123787895356412,
+                345780890878896,
+                97862516286480,
+                25371763481680,
+                5996962277488,
+                1285063345176,
+                247994680648,
+                42757703560,
+                6522361560,
+                869648208,
+                99795696,
+                9657648,
+                766480,
+                47905,
+                2211,
+                67,
+                1
+            ]
+        );
+    }
+
+    #[test]
+    fn test_zip() {
+        assert_eq!(zip(vec![1, 2], vec![4, 5]), vec![(1, 4), (2, 5)]);
+        assert_eq!(zip(vec![1, 2, 3], vec![4, 5]), vec![(1, 4), (2, 5)]);
+        assert_eq!(zip(vec![1, 2], vec![4, 5, 6]), vec![(1, 4), (2, 5)]);
+        assert_eq!(zip(vec![], vec![4, 5]), vec![]);
+    }
+}

src/assignments/assignment02/vec_and_mat.rs

@@ -0,0 +1,121 @@
+//! Vector and matrices.
+//!
+//! You will implement simple operations on vectors and matrices.
+
+use std::ops::Mul;
+
+/// 2x2 matrix of the following configuration:
+///
+/// a, b
+/// c, d
+#[derive(Debug, Clone, Copy)]
+struct Mat2 {
+    a: u64,
+    b: u64,
+    c: u64,
+    d: u64,
+}
+
+/// 2x1 matrix of the following configuration:
+///
+/// a
+/// b
+#[derive(Debug, Clone, Copy)]
+struct Vec2 {
+    a: u64,
+    b: u64,
+}
+
+impl Mat2 {
+    /// Creates an identity matrix.
+    fn new() -> Self {
+        Self {
+            a: 1,
+            b: 0,
+            c: 0,
+            d: 1,
+        }
+    }
+}
+
+impl Mul<Mat2> for Mat2 {
+    type Output = Mat2;
+
+    fn mul(self, rhs: Mat2) -> Self::Output {
+        todo!()
+    }
+}
+
+impl Mul<Vec2> for Mat2 {
+    type Output = Vec2;
+
+    /// Multiplies the matrix by the vector.
+    fn mul(self, rhs: Vec2) -> Self::Output {
+        todo!()
+    }
+}
+
+impl Mat2 {
+    /// Calculates the power of matrix.
+    fn power(self, power: u64) -> Mat2 {
+        todo!()
+    }
+}
+
+impl Vec2 {
+    /// Gets the upper value of vector.
+    fn get_upper(self) -> u64 {
+        todo!()
+    }
+}
+
+/// The matrix used for calculating Fibonacci numbers.
+const FIBONACCI_MAT: Mat2 = Mat2 {
+    a: 1,
+    b: 1,
+    c: 1,
+    d: 0,
+};
+
+/// The vector used for calculating Fibonacci numbers.
+const FIBONACCI_VEC: Vec2 = Vec2 { a: 1, b: 0 };
+
+/// Calculates the Fibonacci number. (We assume the absence of integer overflow.)
+///
+/// Consult <https://web.media.mit.edu/~holbrow/post/calculating-fibonacci-numbers-with-matrices-and-linear-algebra/> for matrix computation of Fibonacci numbers.
+pub fn fibonacci(n: u64) -> u64 {
+    (FIBONACCI_MAT.power(n) * FIBONACCI_VEC).get_upper()
+}
+
+/// 2x2 floating-point matrix of the following configuration:
+///
+/// a, b
+/// c, d
+#[derive(Debug, Clone, Copy)]
+pub struct FMat2 {
+    /// row 1, column 1
+    pub a: f64,
+    /// row 1, column 2
+    pub b: f64,
+    /// row 2, column 1
+    pub c: f64,
+    /// row 2, column 2
+    pub d: f64,
+}
+
+impl FMat2 {
+    /// Returns the inverse of the given matrix. (We assume the given matrix is always invertible.)
+    /// HINT: https://www.mathcentre.ac.uk/resources/uploaded/sigma-matrices7-2009-1.pdf
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// assert_eq!(
+    ///     Mat2 { a: 1.0, b: 1.0, c: 2.0, d: 3.0 }.inverse(),
+    ///     Mat2 { a: 3.0, b: -1.0, c: -2.0, d: 1.0}
+    /// );
+    /// ```
+    pub fn inverse(self) -> Self {
+        todo!()
+    }
+}

src/assignments/assignment02/vec_and_mat_grade.rs

@@ -0,0 +1,60 @@
+#[cfg(test)]
+mod test {
+    use crate::assignments::assignment02::vec_and_mat::*;
+
+    #[test]
+    fn test_fibonacci() {
+        assert_eq!(fibonacci(0), 1);
+        assert_eq!(fibonacci(1), 1);
+        assert_eq!(fibonacci(2), 2);
+        assert_eq!(fibonacci(3), 3);
+        assert_eq!(fibonacci(4), 5);
+        assert_eq!(fibonacci(5), 8);
+        assert_eq!(fibonacci(6), 13);
+        assert_eq!(fibonacci(7), 21);
+        assert_eq!(fibonacci(50), 20365011074);
+        assert_eq!(fibonacci(92), 12200160415121876738);
+    }
+
+    // Equivalence between two floating-point matrices, as element-wise equivalence
+    use std::cmp::PartialEq;
+    impl PartialEq for FMat2 {
+        fn eq(&self, other: &FMat2) -> bool {
+            self.a == other.a && self.b == other.b && self.c == other.c && self.d == other.d
+        }
+    }
+
+    #[test]
+    fn test_inverse() {
+        assert_eq!(
+            FMat2 {
+                a: 1.0,
+                b: 1.0,
+                c: 2.0,
+                d: 3.0
+            }
+            .inverse(),
+            FMat2 {
+                a: 3.0,
+                b: -1.0,
+                c: -2.0,
+                d: 1.0
+            }
+        );
+        assert_eq!(
+            FMat2 {
+                a: 2.0,
+                b: 3.0,
+                c: 5.0,
+                d: 7.0
+            }
+            .inverse(),
+            FMat2 {
+                a: -7.0,
+                b: 3.0,
+                c: 5.0,
+                d: -2.0
+            }
+        );
+    }
+}

src/assignments/assignment02_grade.rs

@@ -1,303 +0,0 @@
-#[cfg(test)]
-mod test {
-    use super::super::assignment02::*;
-
-    #[test]
-    fn test_fahrenheit() {
-        assert_eq!(fahrenheit_to_celsius(32.0), 0.0);
-        assert_eq!(fahrenheit_to_celsius(212.0), 100.0);
-    }
-
-    #[test]
-    fn test_capitalize() {
-        assert_eq!(
-            capitalize(String::from("aAbbBcccCddddD❤한글과✓")),
-            String::from("AABBBCCCCDDDDD❤한글과✓"),
-        );
-        assert_eq!(capitalize(String::from("Tschüß")), String::from("TSCHüß"));
-    }
-
-    #[test]
-    fn test_up3() {
-        assert_eq!(up3(0), 1);
-        assert_eq!(up3(1), 1);
-        assert_eq!(up3(6), 9);
-        assert_eq!(up3(9), 9);
-        assert_eq!(up3(10), 27);
-        assert_eq!(up3(1_000_000), 1_594_323);
-        assert_eq!(up3(3u64.pow(39).wrapping_add(1)), 3u64.pow(40));
-        assert_eq!(up3(3u64.pow(40)), 3u64.pow(40));
-    }
-
-    #[test]
-    fn test_gcd() {
-        assert_eq!(gcd(5, 1), 1);
-        assert_eq!(gcd(3, 3), 3);
-        assert_eq!(gcd(2, 6), 2);
-        assert_eq!(gcd(24, 18), 6);
-        assert_eq!(gcd(20, 63), 1);
-        assert_eq!(gcd(0, 33), 33);
-    }
-
-    #[test]
-    fn test_sum_array() {
-        assert_eq!(sum_array(&[]), 0);
-        assert_eq!(sum_array(&[1]), 1);
-        assert_eq!(sum_array(&[1, 2, 3, 4, 5, 100]), 115);
-    }
-
-    #[test]
-    fn test_chooses() {
-        assert_eq!(chooses(0), vec![1]);
-        assert_eq!(chooses(1), vec![1, 1]);
-        assert_eq!(chooses(5), vec![1, 5, 10, 10, 5, 1]);
-        assert_eq!(chooses(6), vec![1, 6, 15, 20, 15, 6, 1]);
-        assert_eq!(
-            chooses(67),
-            vec![
-                1,
-                67,
-                2211,
-                47905,
-                766480,
-                9657648,
-                99795696,
-                869648208,
-                6522361560,
-                42757703560,
-                247994680648,
-                1285063345176,
-                5996962277488,
-                25371763481680,
-                97862516286480,
-                345780890878896,
-                1123787895356412,
-                3371363686069236,
-                9364899127970100,
-                24151581961607100,
-                57963796707857040,
-                129728497393775280,
-                271250494550621040,
-                530707489338171600,
-                972963730453314600,
-                1673497616379701112,
-                2703342303382594104,
-                4105075349580976232,
-                5864393356544251760,
-                7886597962249166160,
-                9989690752182277136,
-                11923179284862717872,
-                13413576695470557606,
-                14226520737620288370,
-                14226520737620288370,
-                13413576695470557606,
-                11923179284862717872,
-                9989690752182277136,
-                7886597962249166160,
-                5864393356544251760,
-                4105075349580976232,
-                2703342303382594104,
-                1673497616379701112,
-                972963730453314600,
-                530707489338171600,
-                271250494550621040,
-                129728497393775280,
-                57963796707857040,
-                24151581961607100,
-                9364899127970100,
-                3371363686069236,
-                1123787895356412,
-                345780890878896,
-                97862516286480,
-                25371763481680,
-                5996962277488,
-                1285063345176,
-                247994680648,
-                42757703560,
-                6522361560,
-                869648208,
-                99795696,
-                9657648,
-                766480,
-                47905,
-                2211,
-                67,
-                1
-            ]
-        );
-    }
-
-    #[test]
-    fn test_zip() {
-        assert_eq!(zip(vec![1, 2], vec![4, 5]), vec![(1, 4), (2, 5)]);
-        assert_eq!(zip(vec![1, 2, 3], vec![4, 5]), vec![(1, 4), (2, 5)]);
-        assert_eq!(zip(vec![1, 2], vec![4, 5, 6]), vec![(1, 4), (2, 5)]);
-        assert_eq!(zip(vec![], vec![4, 5]), vec![]);
-    }
-
-    #[test]
-    fn test_fibonacci() {
-        assert_eq!(fibonacci(0), 1);
-        assert_eq!(fibonacci(1), 1);
-        assert_eq!(fibonacci(2), 2);
-        assert_eq!(fibonacci(3), 3);
-        assert_eq!(fibonacci(4), 5);
-        assert_eq!(fibonacci(5), 8);
-        assert_eq!(fibonacci(6), 13);
-        assert_eq!(fibonacci(7), 21);
-        assert_eq!(fibonacci(50), 20365011074);
-        assert_eq!(fibonacci(92), 12200160415121876738);
-    }
-
-    // Equivalence between two floating-point matrices, as element-wise equivalence
-    use std::cmp::PartialEq;
-    impl PartialEq for FMat2 {
-        fn eq(&self, other: &FMat2) -> bool {
-            self.a == other.a && self.b == other.b && self.c == other.c && self.d == other.d
-        }
-    }
-
-    #[test]
-    fn test_inverse() {
-        assert_eq!(
-            FMat2 {
-                a: 1.0,
-                b: 1.0,
-                c: 2.0,
-                d: 3.0
-            }
-            .inverse(),
-            FMat2 {
-                a: 3.0,
-                b: -1.0,
-                c: -2.0,
-                d: 1.0
-            }
-        );
-        assert_eq!(
-            FMat2 {
-                a: 2.0,
-                b: 3.0,
-                c: 5.0,
-                d: 7.0
-            }
-            .inverse(),
-            FMat2 {
-                a: -7.0,
-                b: 3.0,
-                c: 5.0,
-                d: -2.0
-            }
-        );
-    }
-
-    #[test]
-    fn test_lyrics() {
-        assert_eq!(twelve_days_of_christmas_lyrics(), LYRICS)
-    }
-
-    const LYRICS: &str = r#"On the first day of Christmas, my true love sent to me
-A partridge in a pear tree
-
-On the second day of Christmas, my true love sent to me
-Two turtledoves
-And a partridge in a pear tree
-
-On the third day of Christmas, my true love sent to me
-Three French hens
-Two turtledoves
-And a partridge in a pear tree
-
-On the fourth day of Christmas, my true love sent to me
-Four calling birds
-Three French hens
-Two turtledoves
-And a partridge in a pear tree
-
-On the fifth day of Christmas, my true love sent to me
-Five gold rings (five golden rings)
-Four calling birds
-Three French hens
-Two turtledoves
-And a partridge in a pear tree
-
-On the sixth day of Christmas, my true love sent to me
-Six geese a-laying
-Five gold rings (five golden rings)
-Four calling birds
-Three French hens
-Two turtledoves
-And a partridge in a pear tree
-
-On the seventh day of Christmas, my true love sent to me
-Seven swans a-swimming
-Six geese a-laying
-Five gold rings (five golden rings)
-Four calling birds
-Three French hens
-Two turtledoves
-And a partridge in a pear tree
-
-On the eighth day of Christmas, my true love sent to me
-Eight maids a-milking
-Seven swans a-swimming
-Six geese a-laying
-Five gold rings (five golden rings)
-Four calling birds
-Three French hens
-Two turtledoves
-And a partridge in a pear tree
-
-On the ninth day of Christmas, my true love sent to me
-Nine ladies dancing
-Eight maids a-milking
-Seven swans a-swimming
-Six geese a-laying
-Five gold rings (five golden rings)
-Four calling birds
-Three French hens
-Two turtledoves
-And a partridge in a pear tree
-
-On the tenth day of Christmas, my true love sent to me
-Ten lords a-leaping
-Nine ladies dancing
-Eight maids a-milking
-Seven swans a-swimming
-Six geese a-laying
-Five gold rings (five golden rings)
-Four calling birds
-Three French hens
-Two turtledoves
-And a partridge in a pear tree
-
-On the eleventh day of Christmas, my true love sent to me
-I sent eleven pipers piping
-Ten lords a-leaping
-Nine ladies dancing
-Eight maids a-milking
-Seven swans a-swimming
-Six geese a-laying
-Five gold rings (five golden rings)
-Four calling birds
-Three French hens
-Two turtledoves
-And a partridge in a pear tree
-
-On the twelfth day of Christmas, my true love sent to me
-Twelve drummers drumming
-Eleven pipers piping
-Ten lords a-leaping
-Nine ladies dancing
-Eight maids a-milking
-Seven swans a-swimming
-Six geese a-laying
-Five gold rings (five golden rings)
-Four calling birds
-Three French hens
-Two turtledoves
-And a partridge in a pear tree
-
-And a partridge in a pear tree
-"#;
-}

src/assignments/assignment03.rs

@@ -1,288 +0,0 @@
-//! Assignment 3: Mastering common programming concepts (2/2)
-//!
-//! You should fill out the `todo!()` placeholders in such a way that `/scripts/grade-03.sh` works fine.
-//! See `assignment03_grade.rs` and `/scripts/grade-03.sh` for the test script.
-
-use std::collections::{HashMap, HashSet};
-use std::fmt;
-
-/// Day of week.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum DayOfWeek {
-    /// Sunday.
-    Sun,
-    /// Monday.
-    Mon,
-    /// Tuesday.
-    Tue,
-    /// Wednesday.
-    Wed,
-    /// Thursday.
-    Thu,
-    /// Friday.
-    Fri,
-    /// Saturday.
-    Sat,
-}
-
-/// The next day of week.
-///
-/// `next_weekday(Thu)` is `Fri`; and `next_weekday(Fri)` is `Mon`.
-pub fn next_weekday(day: DayOfWeek) -> DayOfWeek {
-    todo!()
-}
-
-/// Custom option type.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum MyOption<T> {
-    /// Some value of type `T`.
-    MySome(T),
-    /// No value.
-    MyNone,
-}
-
-/// Maps an `MyOption<T>` to `MyOption<U>` by applying a function to a contained value.
-///
-/// # Examples
-///
-/// Converts an `MyOption<String>` into an `MyOption<usize>`, consuming the original:
-///
-/// ```
-/// use cs220::assignments::assignment03::{my_map, MyOption};
-///
-/// fn len(s: String) -> usize {
-///     s.len()
-/// }
-///
-/// assert_eq!(my_map(MyOption::MySome(String::from("Hello, World!")), len), MyOption::MySome(13));
-/// assert_eq!(my_map(MyOption::MyNone, len), MyOption::MyNone);
-/// ```
-pub fn my_map<T, U, F: FnOnce(T) -> U>(v: MyOption<T>, f: F) -> MyOption<U> {
-    todo!()
-}
-
-/// Returns `MyNone` if the option is `MyNone`, otherwise calls `f` with the wrapped value and returns the result.
-///
-/// Some languages call this operation flatmap.
-///
-/// # Examples
-///
-/// ```
-/// use cs220::assignments::assignment03::{MyOption, my_and_then};
-///
-/// fn pos_then_to_string(x: isize) -> MyOption<String> {
-///     if x > 0 {
-///         MyOption::MySome(x.to_string())
-///     } else {
-///         MyOption::MyNone
-///     }
-/// }
-///
-/// assert_eq!(my_and_then(MyOption::MySome(2), pos_then_to_string), MyOption::MySome(2.to_string()));
-/// assert_eq!(my_and_then(MyOption::MySome(-3), pos_then_to_string), MyOption::MyNone);
-/// assert_eq!(my_and_then(MyOption::MyNone, pos_then_to_string), MyOption::MyNone);
-/// ```
-pub fn my_and_then<T, U, F: FnOnce(T) -> MyOption<U>>(v: MyOption<T>, f: F) -> MyOption<U> {
-    todo!()
-}
-
-/// Given a list of integers, returns its median (when sorted, the value in the middle position).
-///
-/// For a data set `x` of `n` elements, the median can be defined as follows:
-///
-/// - If `n` is odd, the median is `(n+1)/2`-th smallest element of `x`.
-/// - If `n` is even, the median is `(n/2)+1`-th smallest element of `x`.
-///
-/// For example, the following list of seven numbers,
-///
-/// ```ignore
-/// vec![1, 3, 3, 6, 7, 8, 9]
-/// ```
-///
-/// has the median of 6, which is the fourth value. And for this data set of eight numbers,
-///
-/// ```ignore
-/// vec![1, 2, 3, 4, 5, 6, 8, 9]
-/// ```
-///
-/// it has the median of 5, which is the fifth value.
-///
-/// Returns `None` if the list is empty.
-pub fn median(values: Vec<isize>) -> Option<isize> {
-    todo!()
-}
-
-/// Given a list of integers, returns its smallest mode (the value that occurs most often; a hash map will be helpful here).
-///
-/// Returns `None` if the list is empty.
-pub fn mode(values: Vec<isize>) -> Option<isize> {
-    todo!()
-}
-
-/// Converts the given string to Pig Latin. Use the rules below to translate normal English into Pig Latin.
-///
-/// 1. If a word starts with a consonant and a vowel, move the first letter of the word at the end of the word and add "ay".
-///
-/// Example: "happy" -> "appyh" + "ay" -> "appyhay"
-///
-/// 2. If a word starts with multiple consonants, move them to the end of the word and add "ay".
-///
-/// Example: "string" -> "ingstr" + "ay" -> "ingstray"
-///
-/// 3. If a word starts with a vowel, add the word "hay" at the end of the word.
-///
-/// Example: "explain" -> "explain" + "hay" -> "explainhay"
-///
-/// Keep in mind the details about UTF-8 encoding!
-///
-/// You may assume the string only contains lowercase alphabets, and it contains at least one vowel.
-pub fn piglatin(input: String) -> String {
-    todo!()
-}
-
-/// Converts HR commands to the organization table.
-///
-/// If the commands are as follows:
-///
-/// ```ignore
-/// vec!["Add Amir to Engineering", "Add Sally to Sales", "Remove Jeehoon from Sales", "Move Amir from Engineering to Sales"]
-/// ```
-///
-/// The return value should be:
-///
-/// ```ignore
-/// ["Sales" -> ["Amir", "Sally"]]
-/// ```
-///
-/// - The result is a map from department to the list of its employees.
-/// - An empty department should not appear in the result.
-/// - There are three commands: "Add {person} to {department}", "Remove {person} from {department}", and "Move {person} from {department} to {department}".
-/// - If a command is not executable, then it's ignored.
-/// - There is no space in the name of the person and department.
-///
-/// See the test function for more details.
-pub fn organize(commands: Vec<String>) -> HashMap<String, HashSet<String>> {
-    todo!()
-}
-
-/// Custom operator: `option_op_or(v1, v2, f)`
-/// If neither `v1` nor `v2` is `Some`, returns `None`.
-/// If exactly one is `Some`, returns the same `Some` value.
-/// If both are `Some`, apply the values inside `Some` to `f` and wrap the resulting value inside `Some`.
-///
-/// # Examples
-///
-/// ```
-/// fn product(a: i32, b: i32) -> i32 {
-///     a * b
-/// }
-///
-/// assert_eq!(option_op_or(None, None, product), None);
-/// assert_eq!(option_op_or(Some(3), None, product), Some(3));
-/// assert_eq!(option_op_or(Some(3), Some(5), product), Some(15));
-/// ```
-pub fn option_op_or<T, F: FnOnce(T, T) -> T>(v1: Option<T>, v2: Option<T>, f: F) -> Option<T> {
-    todo!()
-}
-
-/// Events in a text editor.
-#[derive(Debug)]
-pub enum TypeEvent {
-    /// A character is typed.
-    Type(char),
-    /// The last character is removed.
-    Backspace,
-    /// The whole string is copied to the clipboard.
-    Copy,
-    /// The string in the clipboard is appended.
-    Paste,
-}
-
-/// Starting from an empty string and an empty clipboard,
-/// processes the given `events` in order and returns the resulting string.
-///
-/// See the test function `test_editor` for examples.
-pub fn use_editor(events: Vec<TypeEvent>) -> String {
-    todo!()
-}
-
-/// Parse the string as a shell command.
-///
-/// Usually, a shell command is whitespace-separated array of strings.
-/// ```text
-/// cat file  -->  ["cat", "file"]
-/// ```
-/// But sometimes, you may want to include whitespaces in each argument.
-/// In that case, you can use quotes.
-/// ```text
-/// ls 'VirtualBox VMs'  -->  ["ls", 'VirtualBox VMs']
-/// ls VirtualBox' 'VMs  -->  ["ls", 'VirtualBox VMs']
-/// ```
-///
-/// For simplicity, you may assume that the string only contains alphanumeric characters, spaces
-/// (" "), and single quotes ("'").
-///
-/// See `test_shell` for more examples.
-pub fn parse_shell_command(command: &str) -> Vec<String> {
-    todo!()
-}
-
-/// Represents a JSON value. See https://en.wikipedia.org/wiki/JSON.
-///
-/// For simplicity, you may assume that numbers are of type `i64`, and strings do not contain
-/// special characters that need to be escaped (e.g. '"', '\n', ...).
-#[derive(Debug, PartialEq, Eq)]
-pub enum JsonValue {
-    /// null
-    Null,
-    /// true, false
-    Boolean(bool),
-    /// integers
-    Number(i64),
-    /// strings
-    String(String),
-    /// array of JSON values
-    Array(Vec<JsonValue>),
-    /// objects
-    Object(HashMap<String, JsonValue>),
-}
-
-/// Parse a string into a JSON value. Returns `Err(())` if it contains syntax errors.
-///
-/// See `test_json` for examples.
-pub fn parse_json(json_string: &str) -> Result<JsonValue, String> {
-    todo!()
-}
-
-impl fmt::Display for JsonValue {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            JsonValue::Null => write!(f, "null"),
-            JsonValue::Boolean(b) => write!(f, "{}", b),
-            JsonValue::Number(n) => write!(f, "{}", n),
-            JsonValue::String(s) => write!(f, "\"{}\"", s),
-            JsonValue::Array(arr) => {
-                write!(f, "[")?;
-                let mut iter = arr.iter();
-                if let Some(item) = iter.next() {
-                    write!(f, "{}", item)?;
-                    for item in iter {
-                        write!(f, ", {}", item)?;
-                    }
-                }
-                write!(f, "]")
-            }
-            JsonValue::Object(obj) => {
-                write!(f, "{{")?;
-                let mut iter = obj.iter();
-                if let Some((key, value)) = iter.next() {
-                    write!(f, "\"{}\": {}", key, value)?;
-                    for (key, value) in iter {
-                        write!(f, ", \"{}\": {}", key, value)?;
-                    }
-                }
-                write!(f, "}}")
-            }
-        }
-    }
-}

src/assignments/assignment03/custom_operators.rs

@@ -0,0 +1,79 @@
+//! You will implement a number of custom operators.
+
+/// Custom option type.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum MyOption<T> {
+    /// Some value of type `T`.
+    MySome(T),
+    /// No value.
+    MyNone,
+}
+
+/// Maps an `MyOption<T>` to `MyOption<U>` by applying a function to a contained value.
+///
+/// # Examples
+///
+/// Converts an `MyOption<String>` into an `MyOption<usize>`, consuming the original:
+///
+/// ```
+/// use cs220::assignments::assignment03::{my_map, MyOption};
+///
+/// fn len(s: String) -> usize {
+///     s.len()
+/// }
+///
+/// assert_eq!(my_map(MyOption::MySome(String::from("Hello, World!")), len), MyOption::MySome(13));
+/// assert_eq!(my_map(MyOption::MyNone, len), MyOption::MyNone);
+/// ```
+pub fn my_map<T, U, F: FnOnce(T) -> U>(v: MyOption<T>, f: F) -> MyOption<U> {
+    todo!()
+}
+
+/// Returns `MyNone` if the option is `MyNone`, otherwise calls `f` with the wrapped value and returns the result.
+///
+/// Some languages call this operation flatmap.
+///
+/// # Examples
+///
+/// ```
+/// use cs220::assignments::assignment03::{MyOption, my_and_then};
+///
+/// fn pos_then_to_string(x: isize) -> MyOption<String> {
+///     if x > 0 {
+///         MyOption::MySome(x.to_string())
+///     } else {
+///         MyOption::MyNone
+///     }
+/// }
+///
+/// assert_eq!(my_and_then(MyOption::MySome(2), pos_then_to_string), MyOption::MySome(2.to_string()));
+/// assert_eq!(my_and_then(MyOption::MySome(-3), pos_then_to_string), MyOption::MyNone);
+/// assert_eq!(my_and_then(MyOption::MyNone, pos_then_to_string), MyOption::MyNone);
+/// ```
+pub fn my_and_then<T, U, F: FnOnce(T) -> MyOption<U>>(v: MyOption<T>, f: F) -> MyOption<U> {
+    todo!()
+}
+
+/// Custom operator: `option_op_or(v1, v2, f)`
+/// If neither `v1` nor `v2` is `Some`, returns `None`.
+/// If exactly one is `Some`, returns the same `Some` value.
+/// If both are `Some`, apply the values inside `Some` to `f` and wrap the resulting value inside `Some`.
+///
+/// # Examples
+///
+/// ```
+/// fn product(a: i32, b: i32) -> i32 {
+///     a * b
+/// }
+///
+/// assert_eq!(option_op_or(None, None, product), None);
+/// assert_eq!(option_op_or(Some(3), None, product), Some(3));
+/// assert_eq!(option_op_or(Some(3), Some(5), product), Some(15));
+/// ```
+pub fn my_option_op_or<T, F: FnOnce(T, T) -> T>(
+    v1: MyOption<T>,
+    v2: MyOption<T>,
+    f: F,
+) -> MyOption<T> {
+    todo!()
+}

src/assignments/assignment03/custom_operators_grade.rs

@@ -0,0 +1,58 @@
+#[cfg(test)]
+mod test {
+    use crate::assignments::assignment03::custom_operators::{MyOption::*, *};
+
+    #[test]
+    fn test_my_map() {
+        fn len(s: &str) -> usize {
+            s.len()
+        }
+
+        fn plus_one(x: isize) -> isize {
+            x + 1
+        }
+
+        fn is_positive(x: f64) -> bool {
+            x > 0.0f64
+        }
+
+        assert_eq!(my_map(MySome("Hello, World!"), len), MySome(13));
+        assert_eq!(my_map(MyNone, len), MyNone);
+
+        assert_eq!(my_map(MySome(1), plus_one), MySome(2));
+        assert_eq!(my_map(MyNone, plus_one), MyNone);
+
+        assert_eq!(my_map(MySome(5.0f64), is_positive), MySome(true));
+        assert_eq!(my_map(MySome(-3.0f64), is_positive), MySome(false));
+        assert_eq!(my_map(MyNone::<f64>, is_positive), MyNone);
+    }
+
+    #[test]
+    fn test_my_and_then() {
+        fn plus_one(x: isize) -> MyOption<isize> {
+            MySome(x + 1)
+        }
+
+        fn none(_: isize) -> MyOption<isize> {
+            MyNone
+        }
+
+        assert_eq!(my_and_then(MySome(1), plus_one), MySome(2));
+        assert_eq!(my_and_then(MySome(1), none), MyNone);
+
+        assert_eq!(my_and_then(MyNone, plus_one), MyNone);
+        assert_eq!(my_and_then(MyNone, none), MyNone);
+    }
+
+    fn product(a: i32, b: i32) -> i32 {
+        a * b
+    }
+
+    #[test]
+    fn test_my_option_op_or() {
+        assert_eq!(my_option_op_or(MyNone, MyNone, product), MyNone);
+        assert_eq!(my_option_op_or(MySome(3), MyNone, product), MySome(3));
+        assert_eq!(my_option_op_or(MyNone, MySome(5), product), MySome(5));
+        assert_eq!(my_option_op_or(MySome(3), MySome(5), product), MySome(15));
+    }
+}

src/assignments/assignment03/mod.rs

@@ -0,0 +1,13 @@
+//! Assignment 3: Mastering common programming concepts (2/2)
+//!
+//! You should fill out the `todo!()` placeholders in such a way that `/scripts/grade-03.sh` works fine.
+//! See `*_grade.rs` and `/scripts/grade-03.sh` for the test script.
+
+pub mod small_problems;
+mod small_problems_grade;
+
+pub mod parse_shell;
+mod parse_shell_grade;
+
+pub mod custom_operators;
+mod custom_operators_grade;

src/assignments/assignment03/parse_shell.rs

@@ -0,0 +1,28 @@
+//! Parsing a shell command.
+//!
+//! Shell commands are text-based instructions that you can enter in a command-line interface (CLI)
+//! to interact with operating systems (e.g. Linux) and others.
+//! For example, you can use the `ls` command to list files in a directory.
+//!
+//! You will parse a given string consists of a small number of shell commands.
+
+/// Parse the string as a shell command.
+///
+/// Usually, a shell command is whitespace-separated array of strings.
+/// ```text
+/// cat file  -->  ["cat", "file"]
+/// ```
+/// But sometimes, you may want to include whitespaces in each argument.
+/// In that case, you can use quotes.
+/// ```text
+/// ls 'VirtualBox VMs'  -->  ["ls", 'VirtualBox VMs']
+/// ls VirtualBox' 'VMs  -->  ["ls", 'VirtualBox VMs']
+/// ```
+///
+/// For simplicity, you may assume that the string only contains alphanumeric characters, spaces
+/// (" "), and single quotes ("'").
+///
+/// See `test_shell` for more examples.
+pub fn parse_shell_command(command: &str) -> Vec<String> {
+    todo!()
+}

src/assignments/assignment03/parse_shell_grade.rs

@@ -0,0 +1,38 @@
+#[cfg(test)]
+mod test {
+    use crate::assignments::assignment03::parse_shell::*;
+
+    #[test]
+    fn test_shell() {
+        assert_eq!(
+            parse_shell_command("cat file"),
+            vec!["cat".to_string(), "file".to_string()]
+        );
+        assert_eq!(
+            parse_shell_command("ls 'VirtualBox VMs'"),
+            vec!["ls".to_string(), "VirtualBox VMs".to_string()]
+        );
+        assert_eq!(
+            parse_shell_command("ls VirtualBox' 'VMs"),
+            vec!["ls".to_string(), "VirtualBox VMs".to_string()]
+        );
+        assert_eq!(
+            parse_shell_command("echo once upon a midnight dreary"),
+            vec![
+                "echo".to_string(),
+                "once".to_string(),
+                "upon".to_string(),
+                "a".to_string(),
+                "midnight".to_string(),
+                "dreary".to_string(),
+            ]
+        );
+        assert_eq!(
+            parse_shell_command("echo 'once upon a midnight dreary'"),
+            vec![
+                "echo".to_string(),
+                "once upon a midnight dreary".to_string(),
+            ]
+        );
+    }
+}

src/assignments/assignment03/small_problems.rs

@@ -0,0 +1,130 @@
+//! Small problems.
+
+use std::collections::{HashMap, HashSet};
+use std::fmt;
+
+/// Day of week.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum DayOfWeek {
+    /// Sunday.
+    Sun,
+    /// Monday.
+    Mon,
+    /// Tuesday.
+    Tue,
+    /// Wednesday.
+    Wed,
+    /// Thursday.
+    Thu,
+    /// Friday.
+    Fri,
+    /// Saturday.
+    Sat,
+}
+
+/// The next day of week.
+///
+/// `next_weekday(Thu)` is `Fri`; and `next_weekday(Fri)` is `Mon`.
+pub fn next_weekday(day: DayOfWeek) -> DayOfWeek {
+    todo!()
+}
+
+/// Given a list of integers, returns its median (when sorted, the value in the middle position).
+///
+/// For a data set `x` of `n` elements, the median can be defined as follows:
+///
+/// - If `n` is odd, the median is `(n+1)/2`-th smallest element of `x`.
+/// - If `n` is even, the median is `(n/2)+1`-th smallest element of `x`.
+///
+/// For example, the following list of seven numbers,
+///
+/// ```ignore
+/// vec![1, 3, 3, 6, 7, 8, 9]
+/// ```
+///
+/// has the median of 6, which is the fourth value. And for this data set of eight numbers,
+///
+/// ```ignore
+/// vec![1, 2, 3, 4, 5, 6, 8, 9]
+/// ```
+///
+/// it has the median of 5, which is the fifth value.
+///
+/// Returns `None` if the list is empty.
+pub fn median(values: Vec<isize>) -> Option<isize> {
+    todo!()
+}
+
+/// Given a list of integers, returns its smallest mode (the value that occurs most often; a hash map will be helpful here).
+///
+/// Returns `None` if the list is empty.
+pub fn mode(values: Vec<isize>) -> Option<isize> {
+    todo!()
+}
+
+/// Converts the given string to Pig Latin. Use the rules below to translate normal English into Pig Latin.
+///
+/// 1. If a word starts with a consonant and a vowel, move the first letter of the word at the end of the word and add "ay".
+///
+/// Example: "happy" -> "appyh" + "ay" -> "appyhay"
+///
+/// 2. If a word starts with multiple consonants, move them to the end of the word and add "ay".
+///
+/// Example: "string" -> "ingstr" + "ay" -> "ingstray"
+///
+/// 3. If a word starts with a vowel, add the word "hay" at the end of the word.
+///
+/// Example: "explain" -> "explain" + "hay" -> "explainhay"
+///
+/// Keep in mind the details about UTF-8 encoding!
+///
+/// You may assume the string only contains lowercase alphabets, and it contains at least one vowel.
+pub fn piglatin(input: String) -> String {
+    todo!()
+}
+
+/// Converts HR commands to the organization table.
+///
+/// If the commands are as follows:
+///
+/// ```ignore
+/// vec!["Add Amir to Engineering", "Add Sally to Sales", "Remove Jeehoon from Sales", "Move Amir from Engineering to Sales"]
+/// ```
+///
+/// The return value should be:
+///
+/// ```ignore
+/// ["Sales" -> ["Amir", "Sally"]]
+/// ```
+///
+/// - The result is a map from department to the list of its employees.
+/// - An empty department should not appear in the result.
+/// - There are three commands: "Add {person} to {department}", "Remove {person} from {department}", and "Move {person} from {department} to {department}".
+/// - If a command is not executable, then it's ignored.
+/// - There is no space in the name of the person and department.
+///
+/// See the test function for more details.
+pub fn organize(commands: Vec<String>) -> HashMap<String, HashSet<String>> {
+    todo!()
+}
+
+/// Events in a text editor.
+#[derive(Debug)]
+pub enum TypeEvent {
+    /// A character is typed.
+    Type(char),
+    /// The last character is removed.
+    Backspace,
+    /// The whole string is copied to the clipboard.
+    Copy,
+    /// The string in the clipboard is appended.
+    Paste,
+}
+
+/// Starting from an empty string and an empty clipboard,
+/// processes the given `events` in order and returns the resulting string.
+///
+/// See the test function `test_editor` for examples.
+pub fn use_editor(events: Vec<TypeEvent>) -> String {
+    todo!()
+}

src/assignments/assignment03/small_problems_grade.rs

@@ -1,6 +1,6 @@
 #[cfg(test)]
 mod test {
-    use super::super::assignment03::*;
+    use crate::assignments::assignment03::small_problems::*;
 
     #[test]
     fn test_next_weekday() {
@@ -13,52 +13,6 @@ mod test {
         assert_eq!(next_weekday(DayOfWeek::Sat), DayOfWeek::Mon);
     }
 
-    #[test]
-    fn test_my_map() {
-        use MyOption::*;
-
-        fn len(s: &str) -> usize {
-            s.len()
-        }
-
-        fn plus_one(x: isize) -> isize {
-            x + 1
-        }
-
-        fn is_positive(x: f64) -> bool {
-            x > 0.0f64
-        }
-
-        assert_eq!(my_map(MySome("Hello, World!"), len), MySome(13));
-        assert_eq!(my_map(MyNone, len), MyNone);
-
-        assert_eq!(my_map(MySome(1), plus_one), MySome(2));
-        assert_eq!(my_map(MyNone, plus_one), MyNone);
-
-        assert_eq!(my_map(MySome(5.0f64), is_positive), MySome(true));
-        assert_eq!(my_map(MySome(-3.0f64), is_positive), MySome(false));
-        assert_eq!(my_map(MyNone::<f64>, is_positive), MyNone);
-    }
-
-    #[test]
-    fn test_my_and_then() {
-        use MyOption::*;
-
-        fn plus_one(x: isize) -> MyOption<isize> {
-            MySome(x + 1)
-        }
-
-        fn none(_: isize) -> MyOption<isize> {
-            MyNone
-        }
-
-        assert_eq!(my_and_then(MySome(1), plus_one), MySome(2));
-        assert_eq!(my_and_then(MySome(1), none), MyNone);
-
-        assert_eq!(my_and_then(MyNone, plus_one), MyNone);
-        assert_eq!(my_and_then(MyNone, none), MyNone);
-    }
-
     #[test]
     fn test_median() {
         assert_eq!(median(vec![]), None);
@@ -166,18 +120,6 @@ mod test {
         );
     }
 
-    fn product(a: i32, b: i32) -> i32 {
-        a * b
-    }
-
-    #[test]
-    fn test_option_op_or() {
-        assert_eq!(option_op_or(None, None, product), None);
-        assert_eq!(option_op_or(Some(3), None, product), Some(3));
-        assert_eq!(option_op_or(None, Some(5), product), Some(5));
-        assert_eq!(option_op_or(Some(3), Some(5), product), Some(15));
-    }
-
     #[test]
     fn test_editor() {
         assert_eq!(
@@ -234,93 +176,4 @@ mod test {
             ""
         );
     }
-
-    #[test]
-    fn test_shell() {
-        assert_eq!(
-            parse_shell_command("cat file"),
-            vec!["cat".to_string(), "file".to_string()]
-        );
-        assert_eq!(
-            parse_shell_command("ls 'VirtualBox VMs'"),
-            vec!["ls".to_string(), "VirtualBox VMs".to_string()]
-        );
-        assert_eq!(
-            parse_shell_command("ls VirtualBox' 'VMs"),
-            vec!["ls".to_string(), "VirtualBox VMs".to_string()]
-        );
-        assert_eq!(
-            parse_shell_command("echo once upon a midnight dreary"),
-            vec![
-                "echo".to_string(),
-                "once".to_string(),
-                "upon".to_string(),
-                "a".to_string(),
-                "midnight".to_string(),
-                "dreary".to_string(),
-            ]
-        );
-        assert_eq!(
-            parse_shell_command("echo 'once upon a midnight dreary'"),
-            vec![
-                "echo".to_string(),
-                "once upon a midnight dreary".to_string(),
-            ]
-        );
-    }
-
-    #[test]
-    fn test_json() {
-        use std::collections::HashMap;
-        let json_str = r#"{
-            "name": "John Doe",
-            "age": 30,
-            "city": "New York",
-            "active": true,
-            "address": {
-                "street": "123 Main St",
-                "zipCode": "10001"
-            },
-            "skills": ["Rust", "Python", "JavaScript"],
-            "organization": null
-        }"#;
-        println!("{}", parse_json(json_str).unwrap());
-        assert_eq!(
-            parse_json(json_str),
-            Ok(JsonValue::Object(HashMap::from([
-                (
-                    "name".to_string(),
-                    JsonValue::String("John Doe".to_string())
-                ),
-                ("age".to_string(), JsonValue::Number(30)),
-                (
-                    "city".to_string(),
-                    JsonValue::String("New York".to_string())
-                ),
-                ("active".to_string(), JsonValue::Boolean(true)),
-                (
-                    "address".to_string(),
-                    JsonValue::Object(HashMap::from([
-                        (
-                            "street".to_string(),
-                            JsonValue::String("123 Main St".to_string())
-                        ),
-                        (
-                            "zipCode".to_string(),
-                            JsonValue::String("10001".to_string())
-                        )
-                    ]))
-                ),
-                (
-                    "skills".to_string(),
-                    JsonValue::Array(vec![
-                        JsonValue::String("Rust".to_string()),
-                        JsonValue::String("Python".to_string()),
-                        JsonValue::String("JavaScript".to_string())
-                    ])
-                ),
-                ("organization".to_string(), JsonValue::Null),
-            ])))
-        );
-    }
 }

src/assignments/mod.rs

@@ -9,9 +9,7 @@
 pub mod assignment01;
 mod assignment01_grade;
 pub mod assignment02;
-mod assignment02_grade;
 pub mod assignment03;
-mod assignment03_grade;
 pub mod assignment04;
 pub mod assignment06;
 pub mod assignment07;