Variables

Variables store values that can be used throughout a program.

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Declaring Variables

Variables are declared using the var keyword.

var number = 42

var name = "Azin"

var enabled = true

Variables are immutable by default. To allow reassignment, use the mut modifier.

var mut counter = 0

counter = counter + 1

A variable declaration consists of:

• the var keyword,
• an optional mut modifier,
• the variable name,
• an optional type annotation,
• an initializer.

Every variable declaration must provide an initializer.

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Type Inference

When an initializer is present, the compiler automatically infers the variable's type.

var count = 10

var message = "Hello"

var letter = 'A'

var value = 3.14

The examples above are inferred as:

count   -> int
message -> string
letter  -> char
value   -> float

Type inference is performed entirely at compile time.

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Explicit Types

A variable's type may be specified explicitly using :.

var score: int = 100

var name: string = "Alex"

var pi: float = 3.14

Explicit type annotations are optional whenever the type can be inferred.

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Mutability

Variables declared with var cannot be modified after initialization.

var value = 10

value = 20 // Error

To allow reassignment, declare the variable with var mut.

var mut value = 10

value = 20

Mutability is explicit to make accidental modification less likely.

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Assignment

Only mutable variables may be assigned new values.

var mut x = 5

x = 10

Assignments must be compatible with the variable's type.

var mut value: float = 10.0

value = 15.5

Assigning a value of an incompatible type results in a compile-time error.

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Variable Scope

Variables are visible only within the scope in which they are declared.

importc "stdio"

fn main: int do
    if true then
        var message = "Hello"

        printf("%s\n", message)
    end

    return 0
end

Variables declared inside a block are not accessible outside that block.

Inner scopes may shadow variables declared in outer scopes.

importc "stdio"

var value = 10

fn main: int do
    var value = 20

    printf("%d\n", value)

    return 0
end

---

Global Variables

Variables may be declared outside of functions.

importc "stdio"

var version = "0.2.0"

fn main: int do
    printf("%s\n", version)

    return 0
end

Global variables are accessible throughout the program.

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Examples

A variable with an inferred type.

var age = 13

A mutable variable.

var mut count = 0

count = count + 1

A variable with an explicit type.

var name: string = "Azin"

A global variable.

importc "stdio"

var version = "0.2.0"

fn main: int do
    printf("%s\n", version)

    return 0
end