2001 Prentice Hall, Inc. All rights reserved. 1 Chapter 18 - WMLScript: Control Structures II...

2001 Prentice Hall, Inc. All rights reserved.

1

Chapter 18 - WMLScript: Control Structures II

Outline18.1 Introduction18.2 Essentials of Counter-Controlled Repetition18.3 for Repetition Structure18.4 Examples Using the for Structure18.5 break and continue Statements18.6 Logical Operators18.7 Structured Programming Summary18.8 Example: A Game of Chance

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Outline1 // Fig. 18.1: counter.wmls2 // Counter-controlled repetition3 4 extern function repetition()5 {6 var counter = 1; // initialization7 8 while ( counter <= 6 ) { // repetition condition9 var result = result + counter + " Times through loop\n";10 11 ++counter; // increment12 }13 14 WMLBrowser.setVar( "output", result );15 WMLBrowser.go( "#card2" );16 }

counter.wmlsLoop 6 times.

Increment counter.

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Outline1 <?xml version = "1.0"?>2 <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.2//EN" 3 "http://www.wapforum.org/DTD/wml12.dtd"> 4 5 6 7 8 <wml>9 <card id = "index" title = "Repetition">10 11 12 <do type = "accept" label = "OK">13 <go href = "counter.wmls#repetition()"/>14 </do>15 16 17 Click OK to run script.18 19 </card>20 21 <card id = "card2" title = "Repetition">22 23 24 <do type = "accept" label = "Back">25 <prev />26 </do>27 28 29 $output 30 31 </card> 32 </wml>

fig18_2.wml

Display results.

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Outline

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Outline1 // Fig. 18.3: counterFor.wmls2 // Counter-controlled repetition3 4 extern function repetition()5 {6 // initialization, repetition condition and incrementing 7 // are all included in the for structure header8 for ( var counter = 1; counter <= 6; ++counter ) {9 var result = result + counter + " Times through loop\n";10 }11 12 WMLBrowser.setVar( "output", result );13 WMLBrowser.go( "#card2" );14 }

counterFor.wmls

Loop 6 times.

Increment counter.

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Outline1 <?xml version = "1.0"?>2 <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.2//EN" 3 "http://www.wapforum.org/DTD/wml12.dtd"> 4 5 6 7 8 <wml>9 <card id = "index" title = "Repetition">10 11 12 <do type = "accept" label = "OK">13 <go href = "counterFor.wmls#repetition()"/>14 </do>15 16 17 Click OK to run script.18 19 </card>20 21 <card id = "card2" title = "Repetition">22 23 24 <do type = "accept" label = "Back">25 <prev />26 </do>27 28 29 $output 30 31 </card> 32 </wml>

fig18_4.wml

Display results.

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Outline

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18.3 for Repetition Structure

for ( var counter = 1; counter <= 6; ++counter )

Initial value of control variable Increment of c ontrol variable

C ontro l variable name Final value o f control variable fo r whic h the c ondition is true

for keyword

Loop-continuation condition

Fig. 18.5 Components of a typical for header.

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18.3 for Repetition Structure

counter <= 6true

false

++c ounter

Establish initial value of control variable

Determine if final value of contro l variable has been reac hed

Body o f loop (this may be many statements)

Increment the c ontrol variable

Body

var counter = 1

Fig. 18.6 Flowcharting a typical for repetition structure.

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Outline1 // Fig. 18.7: sumInt.wmls2 // Summation with for3 4 extern function total() 5 {6 var sum = 0; // running total of addition7 8 for ( var number = 2; number <= 10; number += 2 ) {9 sum += number;10 }11 12 WMLBrowser.setVar( "result", sum );13 WMLBrowser.go( "#result" );14 }

sumInt.wmls

Loop 10 times.

Increment counter by 2.

Calculate total.

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Outline1 <?xml version = "1.0"?>2 <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.2//EN" 3 "http://www.wapforum.org/DTD/wml12.dtd"> 4 5 6 7 8 <wml>9 <card id = "index" title = "Sum of Integers">10 11 12 <do type = "accept" label = "Run">13 <go href = "sumInt.wmls#total()" />14 </do>15 16 17 Click Run to run the script18 19 </card> 20 21 <card id = "result" title = "Sum of Integers">22 23 24 <do type = "accept" label = "Home">25 <prev />26 </do>27 28 29 The sum of the even integers from 2 to 10 is: $result30 31 </card> 32 </wml>

fig18_8.wml

Display results.

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Outline

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Outline1 // Fig. 18.9: calcAmount.wmls2 // Calculating compound interest3 4 extern function calcAmount()5 {6 var principal = 1000; // initial amount of loan7 var rate = .05; // interest rate8 var amount; // total amount of loan9 10 for ( var year = 1; year <= 10; ++year ) {11 var compInt = ( principal * 12 Float.pow( 1.0 + rate, year ) );13 14 amount = amount + year + " | " + 15 Float.round( compInt * 100 ) / 100 + "\n";16 }17 18 WMLBrowser.setVar( "result", amount );19 WMLBrowser.refresh();20 }

calcAmount.wmls

Calculate amount.

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Outline1 <?xml version = "1.0"?>2 <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.2//EN" 3 "http://www.wapforum.org/DTD/wml12.dtd"> 4 5 6 7 8 <wml>9 <card id = "index" title = "Compound Interest">10 <do type = "accept" label = "Calc">11 <go href = "calcAmount.wmls#calcAmount()"/>12 </do>13 14 15 Year Amount 16 $result 17 18 </card> 19 </wml>

fig18_10.wml

Display results.

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Outline

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Outline1 // Fig. 18.11: count1.wmls2 // Using the break statement3 4 extern function counter()5 {6 for ( var count = 1; count <= 10; ++count ) {7 var newCount = newCount + "count is: " + count + " \n";8 9 if ( count == "3" ){10 break; // break out of loop if count equals 311 }12 }13 14 var broke = "Broke out of loop at " + count;15 16 17 WMLBrowser.setVar( "brokeVal", broke );18 WMLBrowser.setVar( "countVal", newCount );19 WMLBrowser.go( "#card2" );20 }

count.wmls

Loop 10 times.

Break out of loop if the value of count is 3.

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Outline1 <?xml version = "1.0"?>2 <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.2//EN" 3 "http://www.wapforum.org/DTD/wml12.dtd"> 4 5 6 7 8 <wml>9 <card id = "index" title = "Break Statement">10 11 12 <do type = "accept" label = "Run">13 <go href = "count1.wmls#counter()" />14 </do>15 16 17 The counter starts at 118 19 </card> 20 21 <card id = "card2" title = "Break Statement">22 23 24 <do type = "accept" label = "Home">25 <prev />26 </do>27 28 29 30 31 $countVal 32 $brokeVal33 34 </card> 35 </wml>

fig10_11.wml

Display results.

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Outline

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Outline1 // Fig. 18.13: count2.wmls2 // Using the break statement3 4 extern function counter()5 {6 for ( var count = 1; count <= 3; ++count ) {7 if ( count == "2" ){8 continue; // skip remaining code if count == 29 }10 11 var newCount = newCount + "count is: " + count + " \n";12 }13 14 var broke = "Used continue to skip printing 2";15 16 17 WMLBrowser.setVar( "brokeVal", broke );18 WMLBrowser.setVar( "countVal", newCount );19 WMLBrowser.go( "#card2" );20 }

count2.wmls

Skip remaining code and continue looping if the value of count is 2.

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Outline1 <?xml version = "1.0"?>2 <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.2//EN" 3 "http://www.wapforum.org/DTD/wml12.dtd"> 4 5 6 7 8 <wml>9 <card id = "index" title = "Cont Statement">10 11 12 <do type = "accept" label = "Run">13 <go href = "count2.wmls#counter()" />14 </do>15 16 17 The counter starts at 118 19 </card>20 21 <card id = "card2" title = "Cont Statement">22 23 24 <do type = "accept" label = "Home">25 <prev />26 </do>27 28 29 30 31 $countVal 32 $brokeVal33 34 </card> 35 </wml>

fig18_14.wml

Display results.

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Outline


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18.6 Logical Operators

expression1 expression2 expression1 && expression2

false false false false true false true false false true true true Fig. 18.15 Truth table for the && (logical AND) operator.

expression1 expression2 expression1 || expression2

false false false false true true true false true true true true Fig. 18.16 Truth table for the || (logical OR) operator.

expression !expression

false true true false Fig. 18.17 Truth table for operator ! (logical negation).

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Outline1 // Fig. 18.18: operators.wmls 2 // Logical operators3 4 extern function logicalAnd()5 {6 // logical AND7 var and = "false && false: " + ( false && false ) + "\n" +8 "false && true: " + ( false && true ) + "\n" +9 "true && false: " + ( true && false ) + "\n" +10 "true && true: " + ( true && true );11 12 WMLBrowser.setVar( "operatorAnd", and );13 WMLBrowser.go( "#card2");14 } // end function logicalAnd15 16 extern function logicalOr()17 {18 // logical OR19 var or = "false || false: " + ( false || false ) + "\n" +20 "false || true: " + ( false || true ) + "\n" +21 "true || false: " + ( true || false ) + "\n" +22 "true || true: " + ( true || true );23 24 WMLBrowser.setVar( "operatorOr", or );25 WMLBrowser.go( "#card3");26 } // end function logicalOR27

operators.wmls

Evaluate using logical AND.

Evaluate using logical OR.

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Outline28 extern function logicalNot()29 {30 // logical NOT31 var not = "!false: " + ( !false ) + "\n" +32 "!true: " + ( !true );33 34 WMLBrowser.setVar( "operatorNot", not );35 WMLBrowser.go( "#card4");36 } // end function logicalNot

operators.wmls

Evaluate using logical NOT.

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Outline1 <?xml version = "1.0"?>2 <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.2//EN" 3 "http://www.wapforum.org/DTD/wml12.dtd"> 4 5 6 7 8 <wml>9 <card id = "index" title = "Logical">10 <do type = "accept" label = "Run">11 <go href = "operators.wmls#logicalAnd()" />12 </do>13 14 15 Click Run to run script.16 17 </card> 18 19 <card id = "card2" title = "And">20 <do type = "accept" label = "Next">21 <go href = "operators.wmls#logicalOr()" />22 </do>23 24 25 $operatorAnd26 27 </card> 28 29 <card id = "card3" title = "Or">30 <do type = "accept" label = "Next">31 <go href = "operators.wmls#logicalNot()" />32 </do>33

fig18_19.wml

Display results of logical AND.

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Outline34 35 $operatorOr36 37 </card> 38 39 <card id = "card4" title = "Not">40 <do type = "accept" label = "Home">41 <go href = "#index" />42 </do>43 44 45 $operatorNot46 47 </card> 48 </wml>

fig18_19.wml

Display results of logical AND.

Display results of logical NOT.

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18.7 Structured Programming Summary

Operators Assoc iativity Type

() left to right parentheses

++ -- ! right to left unary

* / % left to right multiplicative

+ - left to right additive

< <= > >= left to right relational

== != left to right equality

&& left to right logical AND

|| left to right logical OR

?: right to left conditional

= += -= *= /= %= right to left assignment

Fig. 18.20 Precedenc e and assoc ia tivity of the operators d iscussed so far.


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T

F

if struc ture(single selec tion)

TF

if/else struc ture(double se lection)

Sequence Selection

Repetition

T

F

while struc ture

T

F

for struc ture

.

.

Fig. 18.21 WMLScript’s single-entry/single-exit sequence, selection and repetition structures.


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Rules for Forming Structured Programs 1) Begin with the “simplest flowchart” (Fig. 15.22).

2) Any rectangle (action) can be replaced by two rectangles (actions) in sequence.

3) Any rectangle (action) can be replaced by any control structure (sequence, if, if/else, while, or for).

4) Rules 2 and 3 may be applied as often as you like and in any order.

Fig. 18.22 Rules for forming structured programs.

Fig. 18.23 The simplest flowchart.


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.

.

Rule 2 Rule 2 Rule 2

Fig. 18.24 Repeatedly applying rule 2 of Fig. 15.21 to the simplest flowchart.


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Rule 3

Rule 3Rule 3

Fig. 18.25 Applying rule 3 of Fig. 15.21 to the simplest flowchart.


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Stacked building blocks Nested building blocks

Overlapping build ing blocks(Illega l in struc tured programs)

Fig. 18.26 Stacked, nested and overlapped building blocks.

Fig. 18.27 An unstructured flowchart.

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Outline1 // Fig. 18.28: craps.wmls2 // Craps game3 4 // process one roll of the dice5 extern function play()6 {7 var sumOfDice = rollDice(); // sum of the dice8 var gameStatus; // "won", "lost" or "continue"9 var result; // holds the dealer's response10 11 // true if first roll12 var firstRoll = WMLBrowser.getVar( "firstRoll" ); 13 14 // holds sum of first roll15 var myPoint = WMLBrowser.getVar("myPoint"); 16 17 // first roll of the dice18 if ( firstRoll == "true" ) {19 20 if ( sumOfDice == 7 || sumOfDice == 11 ) // win on first roll21 gameStatus = "won";22 else if ( sumOfDice == 2 || sumOfDice == 3 ||23 sumOfDice == 12 ) // lose on first roll24 gameStatus = "lost";25 else26 gameStatus = "continue";27 28 myPoint = sumOfDice; // remember dice sum29 WMLBrowser.setVar( "myPoint", myPoint ) // display dice sum30 WMLBrowser.setVar( "firstRoll", "false" );31 } 32

craps.wmls

Retrieve the value of browser variable firstRoll.

Retrieve the value of browser variable myPoint.

Check to see if first roll of the game.Player wins on 7 or 11 on first roll.

Player loses on 2, 3 or 12 on first roll.

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Outline33 else {34 35 if ( sumOfDice == myPoint ) // win by making point36 gameStatus = "won";37 38 else if ( sumOfDice == 7 ) // lose by rolling seven39 gameStatus = "lost";40 else 41 gameStatus = "continue";42 } 43 44 // sets dealer response based on game status45 if ( gameStatus == "continue" ) 46 result = "Dealer says: Roll Again.";47 else if ( gameStatus == "won" ) {48 result = "Dealer says: You win!";49 WMLBrowser.setVar( "firstRoll", "true" );50 } 51 else if ( gameStatus == "lost" ) {52 result = "Dealer says: You lose!";53 WMLBrowser.setVar( "firstRoll", "true" );54 }55 56 // sets variables to be displayed in card257 WMLBrowser.setVar( "score", sumOfDice ); 58 WMLBrowser.setVar( "myPoint", myPoint );59 WMLBrowser.setVar( "dealer", result );60 61 // redirects user to card262 WMLBrowser.go( "#card2" );63 }64

craps.wmls

If the roll of the dice equals the value of the point, player wins.

If the roll of the dice equals 7, the player loses.

If the roll of the dice does not equal the point or 7, the game continues.

Display the result of current roll.

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Outline65 // returns the sum of the roll of the dice66 extern function rollDice()67 {68 var die1 = Lang.random(5) + 1;69 var die2 = Lang.random(5) + 1;70 var total = die1 + die2;71 72 var dieImage1 = "die" + die1 + ".wbmp";73 var dieImage2 = "die" + die2 + ".wbmp";74 75 WMLBrowser.setVar( "die1", die1 );76 WMLBrowser.setVar( "die2", die2 );77 WMLBrowser.setVar( "dieOne", dieImage1 );78 WMLBrowser.setVar( "dieTwo", dieImage2 );79 80 return total; 81 }

craps.wmlsGenerate two radnom numbers between 1 and to represent each die.

Generate the names of the two images to be displayed.

Calculate the total of the two die.

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Outline1 <?xml version = "1.0"?>2 <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.2//EN" 3 "http://www.wapforum.org/DTD/wml12.dtd">4 5 6 7 8 <wml>9 <card id = "index" title = "Craps Game" newcontext = "true">10 <onevent type = "onenterforward">11 <refresh>12 <setvar name = "firstRoll" value = "true" />13 </refresh>14 </onevent>15 16 <do type = "accept" label = "Roll">17 <go href = "theHouse.wmls#play()" />18 </do>19 20 21 Press roll to start the game.22 23 </card>24 25 <card id = "card2" title = "Results">26 <do type = "accept" label = "Roll Again">27 <go href = "theHouse.wmls#play()"/>28 </do>29 30 <do type = "options" label = "New Game">31 <go href = "#index" />32 </do>33

fig18_29.wml

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Outline34 35 Die 1: <img src = "$dieOne" alt = "Die image" /> 36 Die 2: <img src = "$dieTwo" alt = "Die image" /> 37 The first die: $die1 38 The second die: $die2 39 The sum: $score 40 Point: $myPoint 41 $dealer 42 43 </card>44 </wml>

fig18_29.wmlDisplay images of dice.

Display results of roll.

2001 Prentice Hall, Inc. All rights reserved. 1 Chapter 18 - WMLScript: Control Structures II...

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Transcript of 2001 Prentice Hall, Inc. All rights reserved. 1 Chapter 18 - WMLScript: Control Structures II...