From 871110175be04142faac6c6ef7c05354e796cab3 Mon Sep 17 00:00:00 2001
From: Minseong Jang <minseong.jang@cp.kaist.ac.kr>
Date: Thu, 20 Oct 2022 09:30:00 +0900
Subject: [PATCH] Add assignment 8

---
 scripts/grade-08.sh                   | 33 ++++++++++++++++++
 src/assignments/assignment08.rs       | 48 +++++++++++++++++++++++++++
 src/assignments/assignment08_grade.rs | 30 +++++++++++++++++
 src/assignments/mod.rs                |  2 ++
 4 files changed, 113 insertions(+)
 create mode 100755 scripts/grade-08.sh
 create mode 100644 src/assignments/assignment08.rs
 create mode 100644 src/assignments/assignment08_grade.rs

diff --git a/scripts/grade-08.sh b/scripts/grade-08.sh
new file mode 100755
index 0000000..99b7b27
--- /dev/null
+++ b/scripts/grade-08.sh
@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+
+set -e
+set -uo pipefail
+IFS=$'\n\t'
+
+# Imports library.
+BASEDIR=$(dirname "$0")
+source $BASEDIR/grade-utils.sh
+
+RUNNERS=(
+    "cargo"
+    "cargo --release"
+    "cargo_asan"
+    "cargo_asan --release"
+    "cargo_tsan"
+    "cargo_tsan --release"
+)
+
+# Lints.
+run_linters || exit 1
+
+# Executes test for each runner.
+for RUNNER in "${RUNNERS[@]}"; do
+    echo "Running with $RUNNER..."
+
+    TESTS=("--lib assignment08_grade")
+    if [ $(run_tests) -ne 0 ]; then
+        exit 1
+    fi
+done
+
+exit 0
diff --git a/src/assignments/assignment08.rs b/src/assignments/assignment08.rs
new file mode 100644
index 0000000..05a3cdd
--- /dev/null
+++ b/src/assignments/assignment08.rs
@@ -0,0 +1,48 @@
+//! Assignment 8: First-class functions.
+//!
+//! The primary goal of this assignment is to get used to first-class functions.
+//!
+//! You should fill out the `todo!()` placeholders in such a way that `/scripts/grade-08.sh` works fine.
+//! See `assignment08_grade.rs` and `/scripts/grade-08.sh` for the test script.
+
+/// Returns an anonymous function that applies the given function `f` for `n` times.
+///
+/// For instance, `repeat(3, f)(x)` roughly translates to `f(f(f(x)))`.
+pub fn repeat<T, F: FnMut(T) -> T>(n: usize, mut f: F) -> impl FnMut(T) -> T {
+    todo!()
+}
+
+/// Applies the given function `f` for `i` times for the `i`-th element of the given vector.
+///
+/// For instance, `funny_map(f, [v0, v1, v2, v3])` roughly translates to `[v0, f(v1), f(f(v2)), f(f(f(v3)))]`.
+pub fn funny_map<T, F: Fn(T) -> T>(f: F, vs: Vec<T>) -> Vec<T> {
+    todo!()
+}
+
+/// Either `T1`, or `T2`.
+#[derive(Debug, PartialEq, Eq)]
+pub enum Either2<T1, T2> {
+    /// Case 1.
+    Case1 {
+        /// The inner value.
+        inner: T1,
+    },
+    /// Case 1.
+    Case2 {
+        /// The inner value.
+        inner: T2,
+    },
+}
+
+impl<T1, T2> Either2<T1, T2> {
+    /// Maps the inner value.
+    ///
+    /// If the inner value is case 1, apply `f1`, and if it is case 2, apply `f2`.
+    pub fn map<U1, U2, F1, F2>(self, f1: F1, f2: F2) -> Either2<U1, U2>
+    where
+        F1: FnOnce(T1) -> U1,
+        F2: FnOnce(T2) -> U2,
+    {
+        todo!()
+    }
+}
diff --git a/src/assignments/assignment08_grade.rs b/src/assignments/assignment08_grade.rs
new file mode 100644
index 0000000..e6299ed
--- /dev/null
+++ b/src/assignments/assignment08_grade.rs
@@ -0,0 +1,30 @@
+#[cfg(test)]
+mod test {
+    use super::super::assignment08::*;
+
+    #[test]
+    fn test_repeat() {
+        for i in 0..10 {
+            assert_eq!(42 + 2 * i, repeat(i, |x| x + 2)(42));
+        }
+    }
+
+    #[test]
+    fn test_funny_map() {
+        assert_eq!(
+            vec![0, 3, 6, 9, 12],
+            funny_map(|x| x + 2, vec![0, 1, 2, 3, 4])
+        );
+    }
+
+    #[test]
+    fn test_either2_map() {
+        let v1 = Either2::<u32, f32>::Case1 { inner: 42 };
+        let u1 = Either2::<u32, f32>::Case1 { inner: 43 };
+        assert_eq!(u1, v1.map(|i| i + 1, |f| f + 1.0));
+
+        let v2 = Either2::<u32, f32>::Case2 { inner: 42.0 };
+        let u2 = Either2::<u32, f32>::Case2 { inner: 43.0 };
+        assert_eq!(u2, v2.map(|i| i + 1, |f| f + 1.0));
+    }
+}
diff --git a/src/assignments/mod.rs b/src/assignments/mod.rs
index 5a663d6..0aeb881 100644
--- a/src/assignments/mod.rs
+++ b/src/assignments/mod.rs
@@ -15,3 +15,5 @@ pub mod assignment06;
 mod assignment06_grade;
 pub mod assignment07;
 mod assignment07_grade;
+pub mod assignment08;
+mod assignment08_grade;