Programming instructions

Reference
Project Lead The Way © and Carnegie Mellon Robotics Academy © / For use with VEX
®
Robotics Systems
Random Numbers • 1
Sometimes a behavior will call for a robot to use a random number in one of its measurements.
This may seem strange, but randomness can actually be helpful to a robot in avoiding patterns of
movement that would otherwise get it “stuck”.
task main()
{
bMotorReected[port2]=1;
motor[port3]=127;
motor[port2]=127;
wait1Msec(random(5000));
}
Wait for a random time
The number of milliseconds
that the wait1Msec command
will wait for will be a random
number between 0 and 5000.
This program runs the robot
forward for a random amount
of time up to 5 seconds.
Using Random Numbers
Random numbers is pretty straightforward. Wherever you want the random number to appear,
simply add the code random(maxNumber). Each time the line is run, a random (whole) number
between 0 and the number you entered will ll in the spot where the random() command is.
4000 + random(1000)
Minimum value (as shown: 4000-5000)
Adding the random value “on top of” a
base number lets you get random numbers
between a minimum (the base number) and
a maximum (base+maximum random) value.
Using Other Numbers
If you need something other than whole numbers between zero and something, you may
need to be a little creative...
random(100)/100
Percent (as shown: 0-100% in 1% increments)
Dividing your random value by its own maximum
value normalizes the value so that it always falls
between 0 and 1.
srand(123);
wait1Msec(random(5000));
Set random seed
The srand command sets the random
number seed for this robot. Run with the
same seed, “random” numbers will always be
generated in the same sequence.
Seeds
Computers can’t be truly random. Instead, they try to use a hard-to-predict series of numbers
based off a “seed” value. Under certain circumstances, you may want to set the seed
Random Numbers
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