basic-types.md

dyvil	v0.31.0

Basic Types

The top type: any

Since there is no real super type of reference types and primitive types in the JVM, any is the semantic equivalent of java.lang.Object. That implies that boxing is required to correctly support primitive values. An variable such as

let a: any = 10

gets converted to the Java equivalent, which requires boxing to the java.lang.Integer class:

Object a = Integer.valueOf(10)

The bottom type: none

Similar to how any is the super-type of every other type, none is the sub-type of every type. An expression of type none can thus be assigned to any other type. Every throw statement has this type, and functions that always throw an exception or error can also use it to indicate this property.

func error() -> none = throw new Error()

var i: int = 10
i = error() // valid

var s: String = error() // valid

The null type: null

When the compiler tries to infer the type of an expression that evaluates to null during compile-time (usually null itself), the null type gets inferred. For example, a variable such as

var n = null

Gets inferred to:

var n: null = null

Since the only value that is compatible with the null type is null itself, it is not possible to assign any other value to the variable n.

n = "a" // compilation error - incompatible types

You can use null as the parameter or return type of a function. Expressions of type null can be assigned to Optional or Implicitly Unwrapped Optional Types:

var value: String? = null

func action() -> null { ...; null }

value = action()

The Unit Type: void

The Unit Type void is a special data type in Java and Dyvil that is used to indicate that a function returns no value. It cannot be used as the type of a parameter, field or property.

func action() -> void { ... }

let a = action() // invalid - inferred type 'void' cannot be used as a variable type

let v: void = ??? // invalid

Primitive Data Types

The following primitive types are supported in Dyvil:

Name	Bits / Bytes	Signed	Floating-Point	Wrapper Class
boolean	1 / 1	-	-	java.lang.Boolean
byte	8 / 1	yes	no	java.lang.Byte
short	16 / 2	yes	no	java.lang.Short
char	16 / 2	no	no	java.lang.Character
int	32 / 4	yes	no	java.lang.Integer
long	64 / 8	yes	no	java.lang.Long
float	32 / 4	yes	yes	java.lang.Float
double	64 / 8	yes	yes	java.lang.Double

Primitive Types share the same properties as primitive types in Java. However, there is one important difference: They can be used as generic type arguments, such as List<int>. This is only syntactic sugar though, as it will be converted to List<Int> at runtime, thus not eliminating the need for boxed values.