typedef enum {
    NEPTUNE_LIKE,
    GAS_GIANT,
    TERRESTRIAL,
    SUPER_EARTH,
    UNKNOWN
}PlanetType;

typedef struct {
    char name[30];
    PlanetType type;
    float distanceToEarth;
}Planet;

Planet createPlanet(char name[], PlanetType type, double distance) {
    Planet pl;
    strcpy(pl.name, name);
    pl.distanceToEarth = distance;
    pl.type = type;
    return pl;
}

typedef struct
{
    Planet* elems;      /** dynamic array containing the planets */
    int length;         /**  actual length of the array */
    int capacity;       /**  maximum capacity of the array */
} PlanetRepo;

PlanetRepo createPlanetRepo(int capacity) {
    /// create a new planet repo; the elems field must be dynamically allocated (malloc)
    PlanetRepo r;
    r.capacity = capacity;
    r.length = 0;
    r.elems = (Planet*) malloc(sizeof(Planet)*capacity);
    return r;
}
bool add (PlanetRepo* repo, Planet pl) // adding a planet pl in the Repository
{
int pos = repo->length;
    repo->elems[pos] = pl;
    repo->length++;
    return true; }

bool remove (PlanetRepo* repo, Planet pl) // can't figure out the implementation