Karel Primitive Instructions

1
Karel Primitive Instructions

• Basic tools with which all problems are solved
  (analogies carpentry, geometry)
• move()
• turnLeft()
• putBeeper()
• pickBeeper()
• turnOff()

2
OOP -ness

• object.method1()
• object.method2()
• -where a method acts on the object
• -objects are typically nouns (e.g., karel)
• -methods are typically verbs (e.g., move) and
  represent behavior
• karel.move()

3
move()

• forward only, one block
• Error Shutoff if trying to move into a wall (a
  duh! Look first!) Remember C and div by zero???

4
turnLeft()

• stay at same corner
• turn 90 degrees to the left
• cannot cause an error shutoff

5
pickBeeper()

• picks up beeper on current corner and places in
  beeper bag
• attempted on beeper-less corners causes an error
  shutoff

6
putBeeper()

• take beeper from beeper bag and put down on
  current corner
• attempted with an empty beeper bag causes an
  error shutoff

7
turnOff()

• robot turns off and is incapable of executing
  another instruction until restarted
• the last instruction executed on a robot object

8
Description
public class ur_Robot void move() void
turnOff() void turnLeft() void
pickBeeper() void putBeeper()

• ur_Robot class (the Model-T Robot)

primitive You cant/dont need to define this
class it is in a library for you to use
9
Sample Program

• import kareltherobot.
• public class SampleTest implements Directions
• public static void main(String args)
• ur_Robot karel new ur_Robot(2, 1, East, 0)
  
• karel.move()
• karel.move()
• karel.turnLeft()
• karel.turnOff()
• static
• // code here that you need not worry much
  about

10
Error Classification

• 4-types
• lexical error (compiler catches)
• word not in its dictionary
• syntax error (compiler catches)
• incorrect grammar, punctuation, incorrect
  location of a statement
• execution error (run-time environment catches)
• cant perform what you ask (at run-time)
• intent error (logic - guess who catches this
  one!)
• program terminates successfully junk output,
  however

Which is the hardest type of error to correct?
Why?
11
Now You Try a Short Program on Paper 10 minutes

• start a robot (HBot) at position (1, 1) (a.k.a,
  the origin) facing North and having an infinite
  number of beepers
• Have the robot print (using beepers) the letter
  H (with 3-beeper sides and a 1-beeper bar)
• when done, the robot should be facing North back
  at the origin (leaving the world in its original
  state of being)

12
Programming the HBot together

• Lets go into BlueJ and write the HBot. Well
  cover these items
• Your network drive and staying organized
• Creating a workspace
• Using/reading the API
• Compile vs. Execute
• www.apcomputerscience.com/bluej and setting up
  things at home