Add cpp examples (#659)

* Added C++ robot project examples and set up sub .clang-format for them

* Ran formatter

wpilibcExamples/src/main/cpp/examples/PotentiometerPID/src/Robot.cpp

@@ -0,0 +1,82 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2017 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include <array>
+
+#include <AnalogInput.h>
+#include <IterativeRobot.h>
+#include <Joystick.h>
+#include <PIDController.h>
+#include <Spark.h>
+
+/**
+ * This is a sample program to demonstrate how to use a soft potentiometer and a
+ * PID Controller to reach and maintain position setpoints on an elevator
+ * mechanism.
+ */
+class Robot : public frc::IterativeRobot {
+public:
+	void RobotInit() override { pidController.SetInputRange(0, 5); }
+
+	void TeleopInit() override { pidController.Enable(); }
+
+	void TeleopPeriodic() override {
+		// when the button is pressed once, the selected elevator
+		// setpoint
+		// is incremented
+		bool currentButtonValue = joystick.GetTrigger();
+		if (currentButtonValue && !previousButtonValue) {
+			// index of the elevator setpoint wraps around.
+			index = (index + 1) % (sizeof(kSetPoints) / 8);
+		}
+		previousButtonValue = currentButtonValue;
+
+		pidController.SetSetpoint(kSetPoints[index]);
+	}
+
+private:
+	static constexpr int kPotChannel = 1;
+	static constexpr int kMotorChannel = 7;
+	static constexpr int kJoystickChannel = 0;
+
+	// Bottom, middle, and top elevator setpoints
+	static constexpr std::array<double, 3> kSetPoints = {1.0, 2.6, 4.3};
+
+	/* proportional, integral, and derivative speed constants; motor
+	 * inverted
+	 * DANGER: when tuning PID constants, high/inappropriate values for
+	 * pGain,
+	 * iGain, and dGain may cause dangerous, uncontrollable, or
+	 * undesired behavior!
+	 *
+	 * These may need to be positive for a non-inverted motor
+	 */
+	static constexpr double kP = -5.0;
+	static constexpr double kI = -0.02;
+	static constexpr double kD = -2.0;
+
+	int index = 0;
+	bool previousButtonValue = false;
+
+	frc::AnalogInput potentiometer{kPotChannel};
+	frc::Joystick joystick{kJoystickChannel};
+	frc::Spark elevatorMotor{kMotorChannel};
+
+	/* potentiometer (AnalogInput) and elevatorMotor (Victor) can be used as
+	 * a
+	 * PIDSource and PIDOutput respectively. The PIDController takes
+	 * pointers
+	 * to the PIDSource and PIDOutput, so you must use &potentiometer and
+	 * &elevatorMotor to get their pointers.
+	 */
+	frc::PIDController pidController{
+			kP, kI, kD, &potentiometer, &elevatorMotor};
+};
+
+constexpr std::array<double, 3> Robot::kSetPoints;
+
+START_ROBOT_CLASS(Robot)