Values, names & expressions

A variable is a labeled place for a value

A game needs to remember a score, a player's position, and whether a door is unlocked. Give each fact a clear name. Dim declares the variable; As states what kind of value it can hold; = stores a value.

Option Explicit

Dim HeroName As Text
Dim Score As Number
Dim HasKey As Boolean
Dim Speed As Double

HeroName = "Nova"
Score = 70
HasKey = True
Speed = 2.5

You will also meet Image for pictures, and your own Enum, Type, and Class types. Start with the four kinds above.

Turn rules into expressions

An expression calculates a value. For example, Gems * PointsPerGem calculates the reward for all collected gems. A constant is a named value that cannot be changed while the program runs.

Const PointsPerGem = 10

Dim Gems As Number
Dim Score As Number

Gems = 7
Score = Gems * PointsPerGem
Print Score

Multiplication and division happen before addition and subtraction. Use parentheses whenever they make your intention clearer. In an assignment such as Score = Score + 10, SMILE reads the old score, adds ten, and stores the new result.

Whole numbers and fractional numbers are different

Number means an integer in SMILE 2.0. Writing 7 creates a Number literal; writing 7.0 creates a Double literal. SMILE does not silently change one type into the other. Use ToDouble or ToNumber where you intend a conversion.

Dim Speed As Double
Dim ElapsedMilliseconds As Number
Dim Distance As Double

Speed = 2.5
ElapsedMilliseconds = 200
Distance = Speed * (ToDouble(ElapsedMilliseconds) / 1000.0)
Print Distance

At 2.5 units per second for 200 milliseconds, the distance is 0.5 units. Converting the elapsed time before division keeps that fraction. ToDouble(1 / 2) is 0.0, because the integer division already produced zero. ToDouble(1) / 2.0 is 0.5.

ToNumber(3.9) gives 3; ToNumber(-3.9) gives -3. The fractional part is removed toward zero. Array positions and loop counters still need Number values.

Talk to the player with Text

Text goes inside double quotation marks. Join Text values with +. To print a label beside a number, separate them with a semicolon. SMILE does not turn a Number into Text just because it is next to a Text value.

Dim HeroName As Text
Dim Score As Number

HeroName = "Nova"
Score = 70

Print "Welcome, " + HeroName + "!"
Print "Score: "; Score

Print normally finishes the line. A final semicolon keeps the next output on that same line. A plain Print finishes that line. Text supports Unicode, so names and dialogue can contain more than English letters.

Text_Length("Nova") gives 4. Text_Slice("Nova", 1, 2) gives "ov": start at zero-based character index 1, then take 2 characters. These functions count Unicode scalar values. See the built-in reference for text and conversion functions.

Ask questions with Boolean expressions

A comparison returns True or False. In an assignment, = stores a value. Inside a condition or expression, = checks equality.

And and Or short-circuit from left to right: the right side is skipped if the left side already decides the answer. Text equality is exact: "Nova" and "nova" are different values, even though SMILE variable names are case-insensitive.

An array stores several values under one name

Imagine three score slots in a row. Dim RoundScores[3] As Number makes three Number elements. Their positions, called indices, start at zero.

Const RoundCount = 3

Dim RoundScores[RoundCount] As Number
Dim Total As Number
Dim RoundIndex As Number

RoundScores[0] = 70
RoundScores[1] = 40
RoundScores[2] = 90

For RoundIndex = 0 To RoundCount - 1
    Total = Total + RoundScores[RoundIndex]
End For

Print Total

The For loop visits each valid index and adds its score. The total is 200. You will learn loops on the next page. Array lengths are fixed by positive compile-time Number expressions; they are not a growable list.

Two dimensions are useful for board games. Dim Board[8, 8] As Number creates 64 elements. Board[2, 5] = 1 changes one cell. Both indices must be from 0 to 7. SMILE checks array bounds; an out-of-range access stops the program with an error.

Code that your future self can read

• Use names such as PlayerHealth and PointsPerGem instead of single letters.
• Use ' for comments that explain why a rule exists.
• Put one instruction on each line and indent nested code by four spaces.
• Spell keywords consistently: Dim, Print, End If. SMILE is case-insensitive, but a consistent style helps you read.
• To continue a long expression onto another line, enclose it in balanced parentheses. An array's square brackets do not enable continuation.

Const RoundCount = 4

' Add this after assigning indices 0, 1, and 2:
RoundScores[3] = 60

Next: make decisions, repeat actions, and name your rules →