Variables

Variables are by default dynamically typed, meaning they do not require explicit type declarations. The type of a variable is inferred from the value assigned to it. For more information on types, please see Types.

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var Keyword

The var keyword in Kiwi simplifies variable declaration, supporting multiple styles of initialization with optional type hints.

Syntax

Single variable:

var var_name
var var_name = value
var var_name: type
var var_name: type = value

Multiple variables (grouped with parentheses):

var (<declaration_1>, <declaration_2>, ..., <declaration_n>)

Declaration Options

Each declaration can take one of the following forms: 1. Regular declaration with initialization:

var greeting = "Hello"

- Infers the variable type from the assigned value.

1. Type-hinted declaration with initialization:

   var count: integer = 0
   

2. Specifies the variable type explicitly with an initializer.

3. Union types are supported: var name: type1|type2 = value.

4. Type-hinted declaration without initialization:

   var label: string
   

5. Defaults to the type’s default value (e.g., 0 for integers, false for booleans, "" for strings, null for others).

6. Uninitialized declaration:

   var name
   

7. Defaults to null.

Multiple Declarations

You can group multiple declarations within parentheses () separated by commas ,:

var (x = 10, y: float = 3.14, z: string, w)

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Examples

Single Declaration

var x = 42              # `x` is an integer with the value 42
var name: string        # `name` is a string, defaults to ""
var flag: boolean = true  # `flag` is a boolean with the value true

Multiple Declarations

var (
  age: integer = 25,    # `age` is an integer with value 25
  name = "Kiwi",        # `name` is a string with value "Kiwi"
  is_active: boolean,   # `is_active` is a boolean, defaults to false
  count                 # `count` is uninitialized, defaults to null
)

Practical Example

fn initialize_variables()
  var counter: integer = 0
  var name: string = "Test"
  var active: boolean = true
  var data: list = [1, 2, 3]
  var metadata: hashmap = {"key": "value"}

  return [counter, name, active, data, metadata]
end

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Key Features

1. Type Hints: Declare variables with explicit types for clarity and error prevention.
2. Initialization Flexibility: Mix initialized and uninitialized variables.
3. Compact Syntax: Group related variable declarations with var (...) for cleaner, more maintainable code.

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Use Cases

• Convenient Debugging: Quickly declare multiple variables for experimentation or testing.
• Readable Code: Clearly communicate intent through grouped declarations and type hints.
• Efficient Initialization: Avoid repetitive null initializations or redundant type declarations.

Assigning Variables

You can assign a variable in Kiwi using the = operator.

For example:

a = 10        # Integer assignment
b = 20.5      # Float assignment
c = "Hello"   # String assignment
d = [1, 2, 3] # List assignment

In these cases: - a holds an integer value. - b holds a floating-point number. - c holds a string. - d holds a list of integers.

Variable Reassignment

You can reassign variables at any point, and the type can change based on the new value:

x = 5         # `x` is initially an integer
x = "Kiwi"    # `x` is now a string

Multiple Assignments

Kiwi supports multiple variable assignments using the unpacking syntax =<. This allows assigning multiple values to multiple variables in a single line:

a, b, c =< true, {"a": false}, [1, 2, 3]

Here: - a is assigned the boolean value true. - b is assigned a hashmap with a single key-value pair. - c is assigned a list containing three integers.

This can also be used with functions that return multiple values:

fn get_zero_and_one()
  return [0, 1]
end

zero, one =< get_zero_and_one()

Now, zero is 0 and one is 1.

Variable Scope

Variables in Kiwi are function-scoped, meaning they are only accessible within the function where they are defined unless passed as arguments or returned from a function.

For example:

fn example_scope()
  x = 100  # `x` is only available within this function
end

println(x)  # null

String Interpolation with Variables

Kiwi supports string interpolation, allowing you to embed variable values directly into strings using ${} syntax:

name = "Kiwi"
greeting = "Hello, ${name}!"
println(greeting)  # Hello, Kiwi!

This interpolation works with any valid expression inside ${}.