# Why am I getting an error for my Drive CM Function???

So I’m attempting to make a function for my program to drive a certain number of centimeters using the rotateFor command and I have everything defined but im getting an error that says
15:48:43 – error – error: function definition is not allowed here
void DriveforCm (double DistanceCM, char y) {
^

Why am I getting this error to make the function? Any help would be appreciated

Here’s my code

``````void DriveforCm (double DistanceCM, int veloc) {

//Define variables
double wheelDiameterCM  = 10.16;
double travelTargetCM = DistanceCM; //Wil determine how far the robot goes

//Calc wheel circumferance
double circumference = wheelDiameterCM * M_PI;
double degreesToRotate = (360 * travelTargetCM) / circumference; //All calculations are complete. Start the rest of the program.

//Set the velocity of the left and right motor
LeftDrive.setVelocity(veloc, vex::velocityUnits::pct);
RightDrive.setVelocity(veloc, vex::velocityUnits::pct);

//Rotate the Left and Right Motor for degreesToRotate.
LeftDrive.rotateFor(degreesToRotate, vex::rotationUnits::deg);
RightDrive.rotateFor(degreesToRotate, vex::rotationUnits::deg);

//Stop motors after reached CM distance
LeftDrive.stop
RightDrive.stop
}
``````

Are you declaring it inside main or another function?

Yes I’m declaring in

``````
int Main()

``````

You can’t have have function definitions inside other functions

So moving it out of main should fix it

I did that and it didn’t work

can you post all of the code please

``````vex::competition;

void pre_auton( void ) {
// All activities that occur before the competition starts
// Example: clearing encoders, setting servo positions, ...
void DriveforCM (double DistanceCM, int y) {

//Define variables
double wheelDiameterCM  = 10.16;
double travelTargetCM = DistanceCM; //Wil determine how far the robot goes

//Calc wheel circumferance
double circumference = wheelDiameterCM * M_PI;
double degreesToRotate = (360 * travelTargetCM) / circumference; //All calculations are complete. Start the rest of the program.

//Set the velocity of the left and right motor to 50% power. This command will not make the motor spin.
LeftDrive.setVelocity(y, vex::velocityUnits::pct);
RightDrive.setVelocity(y, vex::velocityUnits::pct);

//Rotate the Left and Right Motor for degreesToRotate.
LeftDrive.rotateFor(degreesToRotate, vex::rotationUnits::deg); //This command must be non blocking.
RightDrive.rotateFor(degreesToRotate, vex::rotationUnits::deg); //This command is blocking so the program will wait here until the right motor is done.

//Stop motors after reached CM distance
LeftDrive.stop
RightDrive.stop
}

}

/*---------------------------------------------------------------------------*/
/*                                                                           */
/*                              Autonomous Task                              */
/*                                                                           */
/*  This task is used to control your robot during the autonomous phase of   */
/*  a VEX Competition.                                                       */
/*                                                                           */
/*  You must modify the code to add your own robot specific commands here.   */
/*---------------------------------------------------------------------------*/

void autonomous( void ) {
// ..........................................................................
// Insert autonomous user code here.
// ........................................................................

}

/*----------------------------------------------------------------------------*/
/*                                                                            */
/*                              User Control Task                             */
/*                                                                            */
/*  This task is used to control your robot during the user control phase of  */
/*  a VEX Competition.                                                        */
/*                                                                            */
/*  You must modify the code to add your own robot specific commands here.    */
/*----------------------------------------------------------------------------*/

void usercontrol( void ) {
// User control code here, inside the loop
while (1)
{
vex::task::sleep(20); //Sleep the task for a short amount of time to prevent wasted resources.
}
}

//
// Main will set up the competition functions and callbacks.
//
int main() {

//Run the pre-autonomous function.
pre_auton();

//Set up callbacks for autonomous and driver control periods.
Competition.autonomous( autonomous );
Competition.drivercontrol( usercontrol );

//Prevent main from exiting with an infinite loop.
while(1) {
vex::task::sleep(100);//Sleep the task for a short amount of time to prevent wasted resources.
}

}
``````

You have

``````
void DriveforCM

``````

inside

``````
void pre_auton

``````

, it needs to be outside of any functions

so something like this:

``````
void DriveforCM (double DistanceCM, int y) {

//Define variables
double wheelDiameterCM  = 10.16;
double travelTargetCM = DistanceCM; //Wil determine how far the robot goes

//Calc wheel circumferance
double circumference = wheelDiameterCM * M_PI;
double degreesToRotate = (360 * travelTargetCM) / circumference; //All calculations are complete. Start the rest of the program.

//Set the velocity of the left and right motor to 50% power. This command will not make the motor spin.
LeftDrive.setVelocity(y, vex::velocityUnits::pct);
RightDrive.setVelocity(y, vex::velocityUnits::pct);

//Rotate the Left and Right Motor for degreesToRotate.
LeftDrive.rotateFor(degreesToRotate, vex::rotationUnits::deg); //This command must be non blocking.
RightDrive.rotateFor(degreesToRotate, vex::rotationUnits::deg); //This command is blocking so the program will wait here until the right motor is done.

//Stop motors after reached CM distance
LeftDrive.stop();
RightDrive.stop();
}

void pre_auton( void ) {
// All activities that occur before the competition starts
// Example: clearing encoders, setting servo positions, ...

DriveforCM(50, 100);
}

``````

Oh so can a void not be inside of a void?

A function of any type cannot have its definition inside any other function

you can still use functions inside other functions, you just cant define in them

Ok thank you

np, if you have any other questions feel free to ask

@abennett5139 “void” and “int” in function declarations and definitions just refer to the data type of the value they return. (You can have ones that return double, *char, int], etc.) They are distinct from what the thing being defined is. Saying

``````
int main () {}

``````

is defining a function with a return value of type int, and your

``````
void DriveforCM (double DistanceCM, int y) {}

``````

is defining a function with a return value of type void (that is, it returns nothing).

Just a question because I know what integers, chars, floats, etc are but what is a double

double is basically 2 x the precision of a float.
eg. if a float variable is using 32 bits, then a double will be using 64 bits.

double precision floating point number.