Why does my token return NULL and how can I fix it?(c++)
- by Van
I've created a program to get a string input from a user and parse it into tokens and move a robot according to the input. The program is supposed to recognize these inputs(where x is an integer): "forward x" "back x" "turn left x" "turn right x" and "stop". The program does what it's supposed to for all commands except for "stop". When I type "stop" the program prints out "whats happening?" because I've written a line which states:
if(token == NULL)
{
cout << "whats happening?" << endl;
}
Why does token get NULL, and how can I fix this so it will read "stop" properly?
here is the code:
bool stopper = 0;
void Navigator::manualDrive()
{
VideoStream video(&myRobot, 0);//allows user to see what robot sees
video.startStream();
const int bufSize = 42;
char uinput[bufSize];
char delim[] = " ";
char *token;
while(stopper == 0)
{
cout << "Enter your directions below: " << endl;
cin.getline(uinput,bufSize);
Navigator::parseInstruction(uinput);
}
}
/* parseInstruction(char *c) -- parses cstring instructions received
* and moves robot accordingly
*/
void Navigator::parseInstruction(char * uinput)
{
char delim[] = " ";
char *token;
// cout << "Enter your directions below: " << endl;
// cin.getline (uinput, bufSize);
token=strtok(uinput, delim);
if(token == NULL)
{
cout << "whats happening?" << endl;
}
if(strcmp("forward", token) == 0)
{
int inches;
token = strtok(NULL, delim);
inches = atoi (token);
double value = fabs(0.0735 * fabs(inches) - 0.0550);
myRobot.forward(1, value);
}
else if(strcmp("back",token) == 0)
{
int inches;
token = strtok(NULL, delim);
inches = atoi (token);
double value = fabs(0.0735 * fabs(inches) - 0.0550);
myRobot.backward(1/*speed*/, value/*time*/);
}
else if(strcmp("turn",token) == 0)
{
int degrees;
token = strtok(NULL, delim);
if(strcmp("left",token) == 0)
{
token = strtok(uinput, delim);
degrees = atoi (token);
double value = fabs(0.00467 * degrees - 0.04);
myRobot.turnLeft(1/*speed*/, value/*time*/);
}
else if(strcmp("right",token) == 0)
{
token = strtok(uinput, delim);
degrees = atoi (token);
double value = fabs(0.00467 * degrees - 0.04);
myRobot.turnRight(1/*speed*/, value/*time*/);
}
}
else if(strcmp("stop",token) == 0)
{
stopper = 1;
}
else
{
std::cerr << "Unknown command '" << token << "'\n";
}
}
/* autoDrive() -- reads in file from ifstream, parses
* and moves robot according to instructions in file
*/
void Navigator::autoDrive(string filename)
{
const int bufSize = 42;
char fLine[bufSize];
ifstream infile;
infile.open("autodrive.txt", fstream::in);
while (!infile.eof())
{
infile.getline(fLine, bufSize);
Navigator::parseInstruction(fLine);
}
infile.close();
}
I need this to break out of the while loop and end manualDrive because in my driver program the next function called is autoDrive.
