Learn to Program with Small Basic

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18 Advanced Text Magic Although pictures of blue skies and green fields are prettier to look at than a screen full of words, many useful programs, such as Facebook, Twitter, and Words with Friends, work with text. That’s why Small Basic provides the Text object for working with text. In this chapter, you’ll learn how to use the Text object to find the length of a string, extract a small portion of a string, and perform many other advanced string-processing tasks. You’ll also write your own string-processing subroutines and apply what you learn to create some interesting applications, like a pig latin translator and a word scramble game! The Text Object You’ve been working with strings throughout this book. To recap, a string is a sequence of characters that is enclosed between double quotes, such as "stringY strinGy striNg strIng stRing". These characters can include letters
(both uppercase and lowercase), digits (0 to 9), and other symbols on your keyboard (such as +, –, &, @, and so on). You can use strings in your programs to store names, addresses, phone numbers, book titles, names of Star Trek episodes, and more. The Text object contains many useful methods for working with strings. Figure 18-1 shows the complete list of the Text object’s methods. We’ve divided these methods into four groups that we’ll discuss in the following sections. Text object Append and length Append(str1, str2) GetLength(str) Case conversion ConvertToLowerCase(str) ConvertToUpperCase(str) Substrings IsSubText(str, sub) EndsWith(str, sub) StartsWith(str, sub) GetSubText(str, pos, len) GetSubTextToEnd(str, pos) GetIndexOf(str, sub) Character codes GetCharacter(code) GetCharacterCode(char) Figure 18-1: The Text object’s methods Appending Strings and Getting Their Length Combining strings and finding their length is a common task in programming. Let’s look at how the Text object can help you out. Appending Strings The Append() method can join (or append) two strings together, as shown in the following example: str = Text.Append("He-", "Man") TextWindow.WriteLine(str) ' Displays: He-Man 264 Chapter 18
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Learn to Program with Small Basic A
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Learn to Program with Small Basic A
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Brief Contents Foreword by Vijaye R
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Exploring Other Features. .........
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7 Empowering Programs with math 83
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12 building Graphical User Interfac
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Storing Records. ..................
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Foreword Computer programming is ma
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Acknowledgments This book represent
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Introduction Have you ever wondered
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• In Chapter 11: Event-Driven Pro
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1 Introducing Small Basic Bill Gate
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BASIC language that would help kids
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Toolbar Help Area Editor Surface Fi
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Then click the New button to open a
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Helping Hands: IntelliSense and Syn
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Programming Challenges If you get s
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The Parts of a Program Let’s expl
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The method’s name and a brief des
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5 + 7 12 Here’s the output of thi
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For example, to make the TextWindow
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TRY IT OUT 2-3 Now you have a chanc
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Programming Errors Just because a p
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26 Chapter 2 4. Write a program tha
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In the system you use at school, po
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Drawing Shapes You can draw lots of
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Figure 3-6 shows what the output lo
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22 GraphicsWindow.BrushColor = "Lig
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DrawText() takes three arguments. T
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GraphicsWindow provides two methods
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6. Write a program that draws this
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4 Using Variables Have you ever wan
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Try changing the value in karenBear
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These two ways of updating the scor
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Figure 4-2: How a variable is added
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TRY IT OUT 4-3 Write a program that
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Two Kinds of Data Programs use all
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5 Drawing Shapes with Turtle Graphi
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Absolute Motion With absolute motio
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North 0 (360) 315 (-45) 45 (-315) W
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GraphicsWindow.PenColor = "Red" Gra
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The For loop runs Turtle.Move(60) a
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y 5). For the hexagon (the polygon
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Creating Polygon Art Using Nested L
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Endless Graphics In Listing 5-10 yo
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Write a program to have the turtle
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Talking to the Computer Until now,
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Figure 6-2: The text window waiting
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4 C = (5 / 9) * (F - 32) 5 C = Math
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9 noun = TextWindow.Read() 10 11 Te
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7 Empowering Programs with Math If
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Here’s a sample run of our progra
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Round() -4 -3.5 -3 0 3 3.5 4 Round(
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This code snippet shows you some ex
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Let’s walk through this program l
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Trigonometric Methods Trigonometric
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Small Basic uses a few different wa
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You can test all sorts of condition
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Small Basic first finds the value o
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Your mom’s instructions assume th
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But wait, your mom just realized th
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This code asks the user to enter a
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9 Using Decisions to Make Games Som
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Condition 1 True Statement set 1 If
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This change to the program means th
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Door 1 Door 2 Door 3 Figure 9-6: Pe
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Listing 9-4 shows an example of usi
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Think of the Shapes object as a “
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Background image (Grid.png) Star.pn
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In Figure 9-8, you see that the gri
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This code asks the player to enter
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10 Solving Problems with Subroutine
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Gulliver later learned that 1 glum-
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TRY IT OUT 10-1 When Gulliver asked
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variables that belong to the main p
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4 TextWindow.WriteLine("Your turn.
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1 step away). If the arrow hits the
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Then you set the graphics window’
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24 Shapes.SetText(msgText, "") 25 T
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Step 8: Shoot Arrows with ShootArro
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Lines 3-7 animate the dragon’s fi
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11 Event-Driven Programming So far,
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GraphicsWindow Events Let’s start
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4 5 Sub OnKeyDown 6 GraphicsWindow.
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13 Else 14 GraphicsWindow.DrawText(
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Useful Tips Before moving on, we’
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21 GraphicsWindow.BrushColor = "Red
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4 XG = Math.GetRandomNumber(8) - 1
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Today, most programs use a graphica
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located at (100, 100). By default,
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9 GraphicsWindow.MouseMove = OnMous
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Let’s look at the computations. Y
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You start by loading the two backgr
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(line 8). If the total resistance i
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TRY IT OUT 12-4 Write a program to
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13 Repeating For Loops Have you eve
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Each For loop starts with the keywo
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The program uses a variable named s
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TRY IT OUT 13-5 What does the follo
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Nested Loops The statements in the
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Figure 13-7: The output of Stamp.sb
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2. Although the pizza in the previo
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In this chapter, you’ll learn how
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Note Although it’s not required b
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asks the user for the correct answe
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to become a value other than 0 (thi
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Step 4: Announce the Winner The las
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15 Grouping Data in One-Dimensional
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One way to think of an array is as
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Page 238 and 239: TextWindow.WriteLine("Enter 5 numbe
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Page 242 and 243: To create this program, we’ll use
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Page 246 and 247: The subroutine uses a For loop to c
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Page 253 and 254: Associative Arrays In the previous
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Page 257 and 258: Here’s the output from a sample r
Page 259 and 260: The ContainsIndex() method takes tw
Page 261 and 262: Figure 16-1 shows the user interfac
Page 263 and 264: 1 Sub OnButtonClicked 2 GraphicsWin
Page 266 and 267: 17 Expanding to Higher-Dimension Ar
Page 268 and 269: 1 ' Random2DArray.sb 2 For r = 1 To
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Page 272 and 273: 12 TextWindow.Write("Enter student
Page 274 and 275: (line 8). Line 9 displays Scott's M
Page 276 and 277: You start by initializing the sum v
Page 278 and 279: 4 For col = 1 To 4 ' For each colum
Page 280 and 281: note If you run into any problems,
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Page 293 and 294: two arguments: the source string th
Page 295 and 296: Here’s an output example: Who's y
Page 297 and 298: More on Code Points The Unicode cod
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Page 307 and 308: When you continue with the second a
Page 309 and 310: TRY IT OUT 18-10 Use the techniques
Page 312 and 313: 19 Receiving File Input and Output
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Page 332 and 333: Where to Go from Here So you’ve m
Page 334 and 335: Index Numbers and Symbols 3DArrayDe
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integrated development environment
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parts of, 14-16 publishing, 5-6 run
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NewGame() subroutine, 255-256 OnBut
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ages 10 and up “Welcome to the ma
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Learn to Program with Small Basic

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