Control Flow Chris Piech CS 106 A Stanford

Control Flow Chris Piech CS 106 A, Stanford University Piech, CS 106 A, Stanford University

CS 106 A Piech, CS 106 A, Stanford University

Karel the Robot s * While Karel is in Java, when you program your Karel assignment we ask that you stick to the concepts in the course reader Piech, CS 106 A, Stanford University

First Challenge 3 + + 2 + + + + 1 2 3 4 Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); turn. Left(); move(); turn. Right(); This is the program's move(); source code put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); turn. Left(); This piece of the program's move(); source code is called a turn. Right(); method. move(); put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); x pick. Beeper(); move(); This line of code gives the turn. Left(); name of the method move(); (here, run) turn. Right(); move(); put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); This line of code gives the turn. Left(); name of the method move(); (here, turn. Right) turn. Right(); move(); put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); turn. Left(); move(); turn. Right(); This is called an import statement. move(); It tells Java what Karel is. put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); This is called a turn. Left(); code block move(); turn. Right(); move(); put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); turn. Left(); move(); turn. Right(); move(); put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); turn. Left(); move(); turn. Right(); move(); put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); turn. Left(); move(); turn. Right(); move(); put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); turn. Left(); move(); turn. Right(); move(); put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); turn. Left(); move(); turn. Right(); The run method is “public” so that move(); Eclipse can call it. put. Beeper(); move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Anatomy of a Program import stanford. karel. *; public class Our. Karel. Program extends Karel { public void run() { move(); pick. Beeper(); move(); turn. Left(); move(); turn. Right(); The turn. Right method is “private” to move(); indicate it is only visible to our put. Beeper(); current program. move(); } } private void turn. Right() { turn. Left(); } Piech, CS 106 A, Stanford University

Piech, CS 106 A, Stanford University

Method Definition private void name() { statements in the method body } ew n a ls ds e d r a a This nd to K a ry m a l m u b co a c o v Piech, CS 106 A, Stanford University

For loops, While loops, If/Else statements Piech, CS 106 A, Stanford University

Place 99 beepers? 99 Piech, CS 106 A, Stanford University

Place 99 beepers public class Place 99 Beepers extends Super. Karel { public void run() { move(); for(int i = 0; i < 99; i++) { put. Beeper(); } move(); } This “for loop” repeats } the code in its “body” 99 times Piech, CS 106 A, Stanford University

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } th e m i t t p o Firs o l he t h g rou Piech, CS 106 A, Stanford University

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } th e m i t t p o Firs o l he t h g rou Piech, CS 106 A, Stanford University

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } th e m i t t p o Firs o l he t h g rou Piech, CS 106 A, Stanford University

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } th e m i t t p o Firs o l he t h g rou Piech, CS 106 A, Stanford University

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University me i t d n Seco the loop gh u o r th

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University me i t d n Seco the loop gh u o r th

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University me i t d n Seco the loop gh u o r th

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University me i t d n Seco the loop gh u o r th

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University e m i t Third he loop t h g u thro

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University e m i t Third he loop t h g u thro

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University e m i t Third he loop t h g u thro

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University e m i t Third he loop t h g u thro

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University e m i t h t Four the loop gh u o r th

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University e m i t h t Four the loop gh u o r th

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University e m i t h t Four the loop gh u o r th

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University e m i t h t Four the loop gh u o r th

Place Beeper Square public class Beeper. Square extends Super. Karel { public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); turn. Left(); } } } Piech, CS 106 A, Stanford University

Exciting! Piech, CS 106 A, Stanford University

Aside: Super Karel import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // super karel has a few more commands turn. Right(); turn. Around(); paint. Corner(BLUE); } put. Beeper(); move(); } Piech, CS 106 A, Stanford University

Next task Piech, CS 106 A, Stanford University

Place Beeper Line Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { } public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); } } Piech, CS 106 A, Stanford University

Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { } public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); } } Piech, CS 106 A, Stanford University

Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { } public void run() { for(int i = 0; i < 4; i++) { put. Beeper(); move(); } } What we want Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { for(int i = 0; i < 3; i++) { put. Beeper(); move(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { for(int i = 0; i < 3; i++) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Actual Bug from Marc II Actual Bug from Mark II Computer Piech, CS 106 A, Stanford University

Grace Hopper Piech, CS 106 A, Stanford University

Don’t Know World Size ? Piech, CS 106 A, Stanford University

Work in Any World Before After Piech, CS 106 A, Stanford University

While Loop Piech, CS 106 A, Stanford University

While Loop import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(condition) { code to repeat } } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Place Beeper Line import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // example while loop while(front. Is. Clear()) { put. Beeper(); move(); } // extra put beeper put. Beeper(); } } Piech, CS 106 A, Stanford University

Piech, CS 106 A, Stanford University

Common misconception: Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University This is incredibly important!

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Place Beeper Line: Redux import stanford. karel. *; public class Beeper. Line extends Super. Karel { public void run() { // place a first beeper put. Beeper(); // example while loop while(front. Is. Clear()) { move(); put. Beeper(); } } } Piech, CS 106 A, Stanford University

Which Loop Repeat Process Don’t know how many times Know how many times For Loop While Loop Piech, CS 106 A, Stanford University

What if you only want to repeat one time? Piech, CS 106 A, Stanford University

If statement Piech, CS 106 A, Stanford University

If Statement import stanford. karel. *; public class If. Example extends Super. Karel { public void run() { // example of an if statement if(condition) { code to run if condition is true } } } Piech, CS 106 A, Stanford University

If Statement import stanford. karel. *; public class If. Example extends Pretend{ public void run() { // example of an if statement if(you. Like. Beyonce()) { make. Some. Noise(); } } } Piech, CS 106 A, Stanford University

If Statement import stanford. karel. *; public class If. Example extends Super. Karel{ public void run() { safe. Move(); } private void safe. Move() { if(front. Is. Clear()) { move(); } } } Piech, CS 106 A, Stanford University

If / Else Statement import stanford. karel. *; public class If. Example extends Super. Karel{ public void run() { invert. Beeper(); } private void invert. Beeper() { if(beepers. Present()) { pick. Beeper(); } else { put. Beeper(); } } } Piech, CS 106 A, Stanford University

The Full Karel Piech, CS 106 A, Stanford University

Random Painter Before: After: Piech, CS 106 A, Stanford University

You just learned most of programming “contro flow” Piech, CS 106 A, Stanford University