memo

1.compile ros:

~/catkin_ws
catkin_make
source devel/setup.bash


2. run ros
rosrun  directory filename
rosrun c_scripts unit2_exercise


3. using namespace std; pour 
    string
    cout
    cin
    endl
4. compile C++
g++ -std=c++11 boring_movie.cpp -o boring_movie_compiled

5.run C++
./boring_movie_compiled


6. 
int* pointer;                   // non-constant pointer to non-constant integer
const int* pointer;             // non-constant pointer to constant integer
int* const pointer;             // constant pointer to non-constant integer
const int* const pointer;       // constant pointer to constant integer

7.
int myarray[4] = {9,99,999,9999};
int* start = myarray;
int* stop = myarray + 4;
int* currentpointer = start;
while (currentpointer != stop) {  ++(*currentpointer);
    ++currentpointer;
}
> 10,100,1000,10000


8.
float *RosbotClass::get_laser_full() {
  float *laser_range_pointer = laser_range.data();
  return laser_range_pointer;
}

/*This function called get_laser_full() is a function that returns a pointer (see the operator asterisk before the name of the class RosbotClass). What it does is take the values of a ROS vector called laser_range and assign them a pointer, then return this pointer. */