cse 111 karel the robot' thanks to dr. kris schindler for this (and all karel the robot slides)

CSE 111

Karel the Robot'

Thanks to Dr. Kris Schindler for this (and all Karel the Robot slides)

Logging into Karel

Available on all cybrary computersFrom home, or in lab use UB Virtual

Computing LabWe will go over this in lab

Guide available at http://www.buffalo.edu/ubit/service-guides/software/my-virtual-computing-lab.html

Linked from course website

Karel’s World

Plain made of streets & avenuesCorners

Describe intersection of streets and avenuesReferenced by

avenue numberstreet number

Avenue & street numbersPositive integers

Origin1st avenue & 1st street

LocationsRelativeAbsolute

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Av en u e s

Stre

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Karel’s World

WallsMade of neutroniumObstacles

Karel cannot pass through a wall

LocationsBetween streetsBetween avenues

Form boundaries on west side & south side

Karel’s World

BeepersPinging beeperSituated at intersectionsCan be

picked upcarriedput down

Karel’s Capabilities

Can Karel the Robot think?Take a look at the path following example

Karel navigates a mazeThe configuration of the maze is unknown to KarelThe end of the maze is determined by a single beeper placed at

the exit


Karel canmove forwardturn in place

Karel knowswhich direction it is facing

Karel is equipped with three cameras

Cameras faceforwardrightleft

Range1/2 block


Karel can hearCan detect a beeper on the same corner Karel is

standing

Karel’s Beeper BagStores beepers

Karel can put beepers in the bag and remove beepers from the bag

SoundproofKarel cannot hear beepers in the bag

Karel’s Tasks

How does Karel know what to do?Karel can follow a detailed set of instructions

Called a program

The language Karel understands is called a programming languageDefined by

vocabularypunctuation marksrules of grammar

Simple, yet powerful

Tasks & Situations

What is a task?Something we want Karel to do

What is a situation?Description of Karel’s worldIncludes

Size & location of each wallLocation & number of beepersKarel’s location & direction Karel is facing

Initial SituationKarel’s world at beginning of task

Includes Karel’s initial location, direction Karel is facing, and the number of beepers in the beeper bag

Final SituationKarel’s world after task is completed

Includes Karel’s final location, direction Karel is facing, and the number of beepers in the beeper bag

Primitive Instructions

Instructionsmoveturnleftpickbeeperputbeeperturnoff

They allow Karel to move through world & handle beepersProvide for avoiding obstacles & transporting

beepers

Program & Instruction Execution

An instruction is executed when Karel performs the action associated with the instruction

A program is executed when the instructions in a program are carried out

Primitive Instruction Details

Changing Positionmove

Karel moves forward one blockKarel remains facing in the same directionIf a wall is in Karel’s way & a move instruction is

executed, Karel shuts off Error shutoff

turnleftKarel pivots 90 degrees to leftLocation does not changeCannot cause error shutoff

Why not?

There is no turnright instructionHow does Karel turn right?


Handling Beeperspickbeeper

Karel picks up a beeper from the corner on which it is standing and deposits the beeper in the beeper bag

Only one beeper is picked upNote that there may be multiple beepers on a corner

What if no beeper exists on the corner?Error shutoff

putbeeperKarel takes a beeper out of beeper bag and places beeper

on cornerWhat if there are not any beepers in the bag?

Error shutoff


Completing a Taskturnoff

Karel must be shut down after task is completedLast instruction in every program

Program Structure

General Structure

BEGINNING-OF-PROGRAMBEGINNING-OF-EXECUTION

Instructions, all but last ending with a semicolon (;)

END-OF-EXECUTION

END-OF-PROGRAM

Executing a Program

Instructions between BEGINNING-OF-EXECUTION and END-OF-EXECUTION sequentially executed until a turnoff instruction or error shutoff is encountered.

Since Karel is a cyber robot, we simulate & trace the programSimulate

Systematically execute program just as Karel would perform each instruction

TraceStep through program, maintaining each step

VerificationSimulation & tracing through program to ensure that it

works properly

Using Karel the Robot in Lab

Enter programCompile programChecks for syntax errors, getting program ready to

run

Setup initial worldInitialize worldExecute programRun

Execution beginsEnds with either:

a proper shutdown (turnoff instruction)a runtime error

TraceStepUnstep

Saving Your Work

Programs and worlds can be saved!

Sample Program

TaskPick up beeper located at intersection of avenue 3,

and street 4

Initial WorldKarel is at the intersection of

avenue 1 and street 1 facing north

Beeper placed at intersection of avenue 3 and street 4

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1K arel’s In itia l

P osition(fac in g n orth )

K arel in itia llyh as zero be epers

in bee per bag

B e eper

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Sample Program

ProgramBEGINNING-OF-PROGRAM

BEGINNING-OF-EXECUTION

turnleft;

turnleft;

turnleft;

move;

move;

turnleft;

move;

move;

move;

pickbeeper;

turnoff

END-OF-EXECUTION

END-OF-PROGRAM

Sample Program

Final World

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K arel’s F in a lP osition

K arel e nds u pw ith on e beepe r

in th e beeper bag

Av en u e s

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SW E

References

Richard E. Pattis (revised by Jim Roberts & mark Stehlik), Karel the Robot, John Wiley & Sons, Inc., 2nd edition, 1995, pp 1-11

Your Task in Lab

Run tutorial, learning how to program using Karel the Robot

cse 111 karel the robot' thanks to dr. kris schindler for this (and all karel the robot slides)

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