Learn to Program with Small Basic

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16 Storing Data with Associative Arrays On social websites like Facebook and LinkedIn, people enter information into text boxes, such as their names, relationship statuses, and even regular updates to their friends (like, “Oh noes!! I just stepped on a bug, and I think I got bug poisoning!”). Programs that need to search or filter this data may use associative arrays to store the various parts of the text. In addition to the indexed arrays you used in Chapter 15, Small Basic supports other types of arrays that can simplify many programming tasks. In this chapter, you’ll start by learning about associative arrays. Then you’ll learn about the Array object, use it to create some fun applications, and even turn your computer into a poet!
Associative Arrays In the previous chapter, you learned how to use an integer index to access an array’s elements. But in Small Basic, an array’s index can also be a string. Arrays indexed by strings are called associative arrays, maps, or dictionaries. In this book, we’ll call them associative arrays. Just like an indexed array, an associative array can store values of any type. You can use an associative array to create an association between a set of keys (string indices) and a set of values, which is called creating a map of key-value pairs. The following code shows a simple example of an associative array in action. It’s a list of states keyed by their two-letter abbreviations: state["CA"] = "California" state["MI"] = "Michigan" state["OH"] = "Ohio" ' ... and so on To display the name of a state, you simply use its corresponding key and the proper syntax. For example, to display Michigan, you can write this statement: TextWindow.WriteLine(state["MI"]) By writing the name of the array followed by the key enclosed in square brackets, you can access the corresponding item. An associative array works like a lookup table that maps keys to values; if you know the key, you can find its value very quickly. To learn how to use associative arrays, let’s write a program that keeps track of the ages of your friends by name. Enter the program in Listing 16-1. 1 ' AssociativeArray.sb 2 age["Bert"] = 17 3 age["Ernie"] = 16 4 age["Zoe"] = 16 5 age["Elmo"] = 17 6 TextWindow.Write("Enter the name of your friend: ") 7 name = TextWindow.Read() 8 TextWindow.Write(name + " is [") 9 TextWindow.WriteLine(age[name] + "] years old.") Listing 16-1: Using associative arrays Lines 2–5 create an associative array named age with four elements in it. You can add more if you’d like, or you can change the array to store the ages of your own friends. Line 6 asks you to enter a friend’s name, and line 7 reads it into the name variable. In line 9, age[name] looks up the age of that friend. 228 Chapter 16
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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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Page 206 and 207: 13 Repeating For Loops Have you eve
Page 208 and 209: Each For loop starts with the keywo
Page 210 and 211: The program uses a variable named s
Page 212 and 213: TRY IT OUT 13-5 What does the follo
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Page 216 and 217: Figure 13-7: The output of Stamp.sb
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Page 221 and 222: In this chapter, you’ll learn how
Page 223 and 224: Note Although it’s not required b
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Page 229 and 230: Step 4: Announce the Winner The las
Page 232 and 233: 15 Grouping Data in One-Dimensional
Page 234 and 235: 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 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
Page 270 and 271: Animated Squares Let’s write a pr
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 291 and 292: Taking Strings Apart: Substrings Ju
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Page 295 and 296: Here’s an output example: Who's y
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Igpay Atinlay Let’s teach the com
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17 TextWindow.WriteLine("Good Job!"
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9 pos = Math.GetRandomNumber(len) '
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When you continue with the second a
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TRY IT OUT 18-10 Use the techniques
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19 Receiving File Input and Output
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and their meanings. File extensions
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program’s folder (right-click the
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in the file would run together in o
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Let’s experiment with the first p
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line number. As with the WriteLine(
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WARNING If the destination path poi
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6 For N = 1 To count ' Displays the
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wizard asks the user to perform. Th
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Figure 19-8 shows a sample run of t
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Where to Go from Here So you’ve m
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Index Numbers and Symbols 3DArrayDe
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squares, 31-32 star, 65-66 triangle
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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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