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Background

Learning objectives

  • Learn how to write functions
  • Learn how to use functions
  • Learn that functions can be called from multiple different locations in your program
  • Learn that the results of one function can pass into another
  • Fly drone across a set of locations in the room

Story

To demolish the outbreak of a new virus in F111, we need you to help us using your drone. We have equipped your drone with our newest high-energy anti-virus weapon, waiting for the FIRE command. Your mission is to hover your drone over the infectious spots (green crosses) and fire your anti-virus weapon by issuing the FIRE command to your program output. You must take off and land your drone in non-infectious areas (blue crosses).

Part I: Coordinate systems

To simplify your mission, we start by creating some simple building blocks - functions.

In this part, you need to write these 6 functions:

  • ftToM: takes one input - number of feet (type double) - convert it to meter.
  • mToFt: takes one input - number of meters (type double) - convert it to feet.
  • polarToCartesianX: takes two input - radius and angle (both type double) - return x value in cartesian coordinate of the corresponding point
  • polarToCartesianY: takes two input - radius and angle (both type double) - return y value in cartesian coordinate of the corresponding point
  • cartesianToPolarRadius: takes two input - x and y (both type double) - return radius value in polar coordinate of the corresponding point
  • cartesianToPolarAngle: takes two input - x and y (both type double) - return angle value (-180 to 180) in polar coordinate of the corresponding point

Note: This is an engineering course - we use degrees for angles, not radians. Specifically, 0 degree is positive x, 90 degree is positive y, 180 degree is negative x, 270 degree is negative y. Also, -90 degree is negative y.

Note: In NO case should the functions output NaN. Your drone will crash if you tell it to fly NaN centimeters!

Hint: You may want Math.atan2(...) and Math.PI. Note that Math.atan2(...) uses radians between -Math.PI and Math.PI. Google is your friend.

To make sure that your mission does NOT fail due to careless mistakes in its building blocks, you need to verify the correctness of your functions.

Write in your main function some program that displays the following report:

ftToM feet=2.0 return=...
ftToM feet=-4.6 return=...
mToFt meters=6.7 return=...
mToFt meters=-3.2 return=...
polarToCartesianX radius=5.0 angle=45.0 return=...
polarToCartesianX radius=5.0 angle=-100.0 return=...
polarToCartesianY radius=5.0 angle=45.0 return=...
polarToCartesianY radius=5.0 angle=-100.0 return=...
cartesianToPolarRadius x=0.0 y=0.0 return=...
cartesianToPolarRadius x=5.0 y=3.0 return=...
cartesianToPolarAngle x=-5.0 y=0.0 return=...
cartesianToPolarAngle x=0.0 y=-5.0 return=...

Show your code and the report to TAs. Commit and push.

Part II: Anti-virus challenge

In this part, you need to write a program that takes user input and flies your drone to the specified location. Specifically, it shall do the following:

  1. Take off your drone
  2. Have the drone fly up another 50cm after the take off height.
  3. Read from user input, and decide what to do:
    1. l: land at the same spot facing the same direction as you took off and exit your program.
    2. c f <x> <y>: hover over the point (cartesian coordinate, feet) and then write FIRE to the screen.
    3. c m <x> <y>: similar as above (cartesian coordinate, meter).
    4. p f <radius> <angle>: similar as above (polar coordinate, feet).
    5. p m <radius> <angle>: similar as above (polar coordinate, meter).
    6. Otherwise, tell the user that the command is invalid, but DO NOT QUIT YOUR PROGRAM. You should read one string from System.in, check if it is l, c, or p. If not, show warning and start over. If the string is l, do what's expected and exit your program. If the string is c or p, read another string from System.in, check if it is f or m. If not, show warning and start over. If the string is f or m, read two real numbers from System.in (you may assume that the user types two real numbers here), and do what's expected. Start over.

The origin is where you take off. Positive lab x-axis points to the right if you stand on a big blue cross and facing a big green cross. Positive lab y-axis points to the front of your drone before taking off. Remember, in polar coordinates, 0 degree is positive x, 90 degree is positive y, 180 degree is negative x, 270 degree is negative y. Note that the drone's method calls only accept positive angles.

Important Note: User ALWAYS types in global (absolute) coordinates. It's your responsibility to transform it to drone commands. Note that you will need to keep a set of current location variables.

Important Note: You may choose to rotate or not rotate your drone. You get different grades based on the way you accomplish your mission. If you do rotate your drone, be sure to rotate it back before landing. Also, the oritentation of the coordinate system NEVER changes once you take off.

Note: To tell user something went wrong, use System.err.println. Writing anything except FIRE to System.out.println may turn the anti-virus weapon into an uncontrollable beast. If you are interested in the differnence among System.in, System.out, and System.err, you may consult this or this.

Note: To minimize rounding errors, please leverage Math.round(...) when converting double to int.

Hint: You may use the drone.move(...) command (see Cheat Sheet). Be aware of couple details if you you move:

  1. All coordinates provided as parameters to move are relative to the current position of a drone
  2. When a drone is placed on the big blue cross and its camera faces the big green cross, positive lab y-axis points the same direction. However, positive drone's y-axis (expected in move command) points into the white wall (to the left if you look from the top and toward the big green cross).

Hint: You SHOULD reuse the functions you have created in Part 1. You need two variables to store your current location and, if you rotate your drone, one additional variable to store your drone's orientation.

Hint: Math in polar coordinate is hard. Math in cartesian coordinate is easy. Google is your friend.

Hint: You may create more functions if you want.

Show your code and demonstrate your result to TAs. The TAs will type in a sequence of absolute points in mixtures of units. Commit and push.

As a bonus, if you want to rotate and fly forward, flying the shortest path, you will get some bonus points. Note that this is not required and you can use the drone.move(...) command for full credit. Turning and flying forward is more difficult as you need convert relative offsets to polar and track you current angle with a variable.

Report from the scout

Thanks to the scout we sent out earlier this week, we have located the exact location of the virus. If you take off at the big blue cross, coordinates of the five green crosses are:

Description c f <x> <y> c m <x> <y> p f <radius> <angle> p m <radius> <angle>
Right most c f 7 6 c m 2.3 2 p f 9 41 p m 3 41
Front right c f 1.5 3 c m 0.5 1 p f 3.4 63 p m 1.1 63
Middle (big) c f 0 10 c m 0 3.5 p f 10 90 p m 3.5 90
Front left c f -1.5 3 c m -0.5 1 p f 3.4 117 p m 1.1 117
Left most c f -7 6 c m -2.3 2 p f 9 139 p m 3 139