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‎assignment6/README.md‎

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# Assignment 6: Explore Courses
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Due Saturday, November 22nd at 11:59PM
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## Overview
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In this assignment you will be exercising your understanding of `std::optional`. We'll be making use of the same `courses.csv` from assignment 1. You are tasked to write one function for this assignment, which attempts to find the a `Course` in the `CourseDatabase` object, and return it.
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You'll also explore the monadic operations that come with the `std::optional` class. Take a look at the code and review the `CourseDatabase` class to understand the interface.
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## Running your code
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To run your code, first you'll need to compile it. Open up a terminal (if you are using VSCode, hit <kbd>Ctrl+\`</kbd> or go to **Terminal > New Terminal** at the top). Then make sure that you are in the `assignment6/` directory and run:
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```sh
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g++ -std=c++23 main.cpp -o main
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```
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Assuming that your code compiles without any compiler errors, you can now do:
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```sh
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./main
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```
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which will actually run the `main` function in `main.cpp`.
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As you are following the instructions below, we recommend intermittently compiling/testing with the autograder as a way to make sure you're on the right track!
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> [!NOTE]
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>
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> ### Note for Windows
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>
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> On Windows, you may need to compile your code using
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>
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> ```sh
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> g++ -static-libstdc++ -std=c++23 main.cpp -o main
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> ```
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>
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> in order to see output. Also, the output executable may be called `main.exe`, in which case you'll run your code with:
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>
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> ```sh
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> ./main.exe
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> ```
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## Part 0: Include `<optional>`
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At the top of the `main.cpp` include `<optional>`, we're going to make use of `std::optional` in this assignment!
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## Part 1: Write the `find_course` function
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This function takes in a string `course_title`, and the function should try to find the `course` inside of the private `courses` member of the `CourseDatabase` object. What should the return type be? (hint: there may or may not be a `Course` for the `course_title` passed in)
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> [!NOTE]
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> You need to change the type returned by `find_course` which is currenty `FillMeIn`.
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## Part 2: Modifying the `main` function
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Notice that we call the `find_course` here in the `main` function:
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```cpp
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auto course = db.find_course(argv[1]);
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```
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Now, you need to make use of the [monadic operations](https://en.cppreference.com/w/cpp/utility/optional) to populate the `output` string properly. Let's walk through how to do this.
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Here's the behavior that you want to recreate, **without using any conditionals** like `if` statements:
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```cpp
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if (course.has_value()) {
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std::cout << "Found course: " << course->title << ","
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<< course->number_of_units << "," << course->quarter << "\n";
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} else {
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std::cout << "Course not found.\n";
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}
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```
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Very simply, if there is a course then the line at the bottom of `main`
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```cpp
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std::cout << output << std::end;
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```
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Should produce:
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```bash
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Found course: <title>,<number_of_units>,<quarter>
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```
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if there is no course then
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```cpp
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std::cout << output << std::end;
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```
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Should produce:
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```bash
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Course not found.
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```
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### Monadic Operations
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There are three monadic operations: [`and_then`](https://en.cppreference.com/w/cpp/utility/optional/and_then), [`transform`](https://en.cppreference.com/w/cpp/utility/optional/transform), and [`or_else`](https://en.cppreference.com/w/cpp/utility/optional/or_else). Read the description of each of them in the lecture slides, and take a look at [the standard library documentation](https://en.cppreference.com/w/cpp/utility/optional). You will only need to use 2 of the mondadic operations.
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Your code should end up looking something like this:
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```cpp
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std::string output = course
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./* monadic function one */ (/* ... */)
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./* monadic function two */ (/* ... */)
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.value(); // OR `.value_or(...)`, see below
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```
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It can help to **think about what the type of `output` is and work backwards from there**. Pay attention to what each of the monadic functions does, as described in the hint below.
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> [!NOTE]
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> Recall what the role is of each of the monadic functions. The official C++ library doesn't do a good job explaining this, so we have included a short reference here. Suppose `T` and `U` are arbitrary types.
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>
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> ```cpp
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> /**
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> * tl;dr;
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> * Calls a function to produce a new optional if there is a value; otherwise, returns nothing.
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> *
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> * The function passed to `and_then` takes a non-optional instance of type `T` and returns a `std::optional<U>`.
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> * If the optional has a value, `and_then` applies the function to its value and returns the result.
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> * If the optional doesn't have a value (i.e. it is `std::nullopt`), it returns `std::nullopt`.
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> */
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> template <typename U>
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> std::optional<U> std::optional<T>::and_then(std::function<std::optional<U>(T)> func);
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>
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> /**
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> * tl;dr;
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> * Applies a function to the stored value if present, wrapping the result in an optional, or returns nothing otherwise.
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> *
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> * The function passed to `transform` takes a non-optional instance of type `T` and returns a non-optional instance of type `U`.
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> * If the optional has a value, `transform` applies the function to its value and returns the result wrapped in an `std::optional<U>`.
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> * If the optional doesn't have a value (i.e. it is `std::nullopt`), it returns `std::nullopt`.
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> */
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> template <typename U>
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> std::optional<U> std::optional<T>::transform(std::function<U(T)> func);
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>
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> /**
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> * tl;dr;
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> * Returns the optional itself if it has a value; otherwise, it calls a function to produce a new optional.
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> *
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> * The opposite of `and_then`.
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> * The function passed to `or_else` takes in no arguments and returns a `std::optional<U>`.
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> * If the optional has a value, `or_else` returns it.
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> * If the optional doesn't have a value (i.e. it is `std::nullopt`), `or_else invokes the function and returns the result.
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> */
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> template <typename U>
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> std::optional<U> std::optional<T>::or_else(std::function<std::optional<U>(T)> func);
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> ```
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>
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> For example, given a `std::optional<T> opt` object, the monadic operations could be invoked as follows:
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>
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> ```cpp
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> opt
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> .and_then([](T value) -> std::optional<U> { return /* ... */; })
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> .transform([](T value) -> U { return /* ... */; });
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> .or_else([]() -> std::optional<U> { return /* ... */; })
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> ```
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>
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> <sup>Note that the `->` notation in the lambda function is a way of explicitly writing out the return type of the function!</sup>
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>
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> Notice that since each method returns an `std::optional`, you can chain them together. If you are certain that the optional will have a value at the end of the chain, you could call [`.value()`](https://en.cppreference.com/w/cpp/utility/optional/value) to get the value. Otherwise, you could call [`.value_or(fallback)`](https://en.cppreference.com/w/cpp/utility/optional/value_or) to get the result or some other `fallback` value if the optional doesn't have a value.
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## 🚀 Submission Instructions
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If you pass all tests, you are ready to submit! To submit the assignment:
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1. Please complete the feedback form [at this link](https://forms.gle/aGuFqLyhB18mNoPKA).
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2. Submit your assignment on [Paperless](https://paperless.stanford.edu)!
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Your deliverable should be:
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- `main.cpp`
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You may resubmit as many times as you'd like before the deadline.

‎assignment6/autograder/autograder.py‎

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from utils import Autograder, ASSIGNMENT_DIR
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from typing import List
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import os
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import subprocess
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def get_main_exe_path() -> os.PathLike:
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main_path = os.path.join(ASSIGNMENT_DIR, "main")
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if not os.path.isfile(main_path):
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main_path = os.path.join(ASSIGNMENT_DIR, "main.exe")
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if not os.path.isfile(main_path):
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raise RuntimeError(
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"Could not find a main executable. Did you compile your code with the command in the README?"
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)
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return main_path
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def verify_output(courses: List[str], found: bool):
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main_path = get_main_exe_path()
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course_names = [course.split(",")[0] for course in courses]
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for course_name, course in zip(course_names, courses):
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result = subprocess.run(
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[main_path, course_name],
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stdout=subprocess.PIPE,
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stderr=subprocess.PIPE,
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text=True,
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)
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if result.returncode != 0:
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raise RuntimeError(result.stderr)
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actual = result.stdout.strip()
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expected = f"Found course: {course}" if found else "Course not found."
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if actual != expected:
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raise RuntimeError(
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f"For course {course_name}, expected output:\n\t{expected}\nbut got:\n\t{actual}"
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)
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if __name__ == "__main__":
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grader = Autograder()
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grader.add_part(
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"Present Courses",
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lambda: verify_output(
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[
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"Introduction to Mobile Augmented Reality Design and Development,1,2023-2024 Spring",
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"Design for Play (SYMSYS 195G),4,2023-2024 Spring",
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"Practical Machine Learning,4,null",
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"Human-Centered AI,3,null",
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"Seminar in Artificial Intelligence in Healthcare,1,2023-2024 Autumn",
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"Introduction to Python Programming,1,2023-2024 Autumn",
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"Machine Learning for Discrete Optimization (MS&E 236),3,2023-2024 Spring",
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"AI for Social Good,2,2023-2024 Spring",
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"Software Project Experience with Corporate Partners,4,2023-2024 Winter",
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"The Future of Mechanical Engineering (ME 228),1,null",
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],
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True,
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),
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)
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grader.add_part(
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"Missing Courses",
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lambda: verify_output(
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[
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"Introduction to Quantum Mechanics for Engineers",
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"Fundamentals of Blockchain and Cryptography",
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"Applied Data Science for Social Impact",
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"Advanced Robotics and Autonomous Systems",
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"Neural Networks and Deep Learning Fundamentals",
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"Exploring the Future of Artificial General Intelligence",
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"Data Ethics and Privacy in the Digital Age",
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"Introduction to Cloud Computing with AWS",
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"Creative Coding for Interactive Media",
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"Virtual Reality and Augmented Reality for Healthcare",
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],
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False,
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),
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)
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grader.run(),

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