- C: Everything is pass-by-value
- Simple example of params vvv

  void swap(int a, int b) {
    int tmp = a;
    a = b;
    b = tmp;
  }

  int a = 1;
  int b = 2;
  swap(a, b);

- Simple example of return vals

  typedef struct {
    double x;
    double y;
  } Point;

  Point create(double a, double b) {
    Point p1 = {.x = a, .y = b}
    return p1;
  }

- What about arrays? Possible not to pass by pointer?

- Remember not to pass back pointers into this stack frame!!!

  Point* create(double a, double b) {
    Point p1 = {.x = a, .y = b}
    return &p1; //NOT GOOD USE MALLOC INSTEAD
  }

- Java: Everything pass-by-value
  - All primitives pass by value (ie ints, boolean)
  - All objects are *pointers* passed by value

    public Point swapX(Point a, Point b) {
      double tmp = a.x;
      a.x = b.x;
      b.x = tmp;
      return a;
    }

    Point* swapX(Point* a, Point* b) {
      double tmp = a->x;
      a->x = b->x;
      b->x = tmp;
      return a;
    }

- C++: Teaser, pass by reference is a thing! Use & instead of *

- HW2: What is it?
  - Implement a 2D array library...from scratch: Must support:
    - Generic objects to store
    - Way to edit the locations of objects in array
    - Must have no leaks
  - Some design decisions:
    - How to implement array itself?

      1st: Single pointer
        - allocation:
            a rows, b columns
            int* arr = (int*) malloc(a * b * sizeof(int));

        - Usage:
          a[i * num_cols + j]

      2nd: Pointers to pointers
        - allocation:
            a rows, b columns
            int** arr = (int**) malloc(a * sizeof(int*));
            for (int i = 0; i < b; i++)
              arr[i] = (int*) malloc(b * sizeof(int));

        - Usage:
            arr[i][j];

      3rd: Double pointer to all rows
        - allocation:
            a rows, b columns
            arr  = (int **)malloc(a * sizeof(int*));
            arr[0] = (int *)malloc(b * a * sizeof(int));

            for(i = 0; i < r; i++)
              arr[i] = (*arr + c * i);
        - Usage:
            arr[i][j]

    - How to implement generics?
      - void *!!
    - What functions to implement?
      - Get and Set are a must!
      - Think about what you might need for candy crush
    - How to handle errors?
      - Pass back as return value?
      - Pass back as return parameter?
      - Creating something like errno? (suggest only)
  - Also an exercise about how to read Documentation
    - What is serialization / deserialization?
        - A way to store data that your program makes in a file 
        - A way to read in data from a file
    - Jansson JSON loader library
      - Number, Boolean, String, Object, Array
    - Example input:
        {
          "rows": 2,
          "columns":3,
          "data":[0,1,2,3,4,5] <--- these can be anything
                                    (client binary can expect int's)
                                    (library must support anything!)
        }
    - How does Jansson work?
        json_load_file() returns root json object
        memory management? reference counters
        use json_decref() to indicate finished with object
    - Functions you might want to look at:
        json_is_object(), json_object_get()
        json_is_integer(), json_integer_value()
        json_is_array(), json_array_get()