Types

Supported types

Type	Description	Literal examples
Int	32-bit signed integer	42, 0xFF, 0b1010, 1_000
Long	64-bit signed integer	100L, 0xFFL, 9999999999L
Double	64-bit floating-point	3.14, 2.5e10, 1.0f, -0.5
String	UTF-8 string	"hello", """raw""", "$x"
Boolean	True or false	true, false
Char	Single character	'A', '\n'
Unit	No meaningful value	Implicit void return
Any	Top type (supertype of all types)	—
null	Null reference	null

Type inference

Skotch infers types from literal initializers:

val x = 42           // Int
val pi = 3.14        // Double
val s = "hello"      // String
val b = true         // Boolean
val n = null         // null

Explicit type annotations are also supported:

val x: Int = 42
val s: String = "hello"

Double arithmetic

Double supports all arithmetic operators, and mixed Int/Double arithmetic promotes to Double:

fun main() {
    val a = 3.0
    val b = 2.0
    println(a + b)    // 5.0
    println(a * b)    // 6.0
    println(a / b)    // 1.5
    println(-2.5)     // -2.5
    println(1.0e2)    // 100.0
}

Type annotations

Function parameters require explicit types. Return types can be inferred for expression-body functions.

fun add(a: Int, b: Int) = a + b    // return type Int inferred
fun greet(name: String): String {  // explicit return type
    return "Hello, $name"
}

Not yet supported

Caution

The following type system features are recognized by the parser but not yet compiled.

Feature	Status
Nullable operators (?., ?:, !!)	Implemented — safe calls, elvis, non-null assertion
Type checks (is/!is)	Implemented — emits instanceof with JVM type descriptors
Smart casts	Implemented — when/if branch narrowing with checkcast + unbox for primitives
Type casts (as/as?)	Parsed; safe cast (as?) returns null on failure
Generics (T, List<Int>)	Implemented — type parameters, bounds, variance (in/out), star projection, reified
Nothing	Implemented — bottom type, assignable to all types
Type aliases	Implemented — typealias erased to underlying type
Char type	Implemented — Ty::Char with CharLit token, println('K') prints K, s[i] returns Char