Functions

Functions are declared with function.

For exact signature, parameter-mode, overload, and result rules, see the Functions reference.

function Add(a : int, b : int) -> int:
    return a + b
endfunc

When there is no return value, omit ->.

function Log(value : int):
    // ...
endfunc

Declarations and Definitions

A function signature may be declared without a body.

function Add(a : int, b : int) -> int

The definition provides the body.

function Add(a : int, b : int) -> int:
    return a + b
endfunc

External functions are declarations connected to symbols outside DQ.

function printf(fmt : ^char, ...) -> int  [[external]]

Return Values

Functions with a return type have a built-in result variable.

function Add(a : int, b : int) -> int:
    result = a + b
endfunc

return value is also supported.

function Add(a : int, b : int) -> int:
    return a + b
endfunc

Parameters

The default parameter mode is by value.

function IncCopy(value : int) -> int:
    return value + 1
endfunc

Reference parameter modes are:

Mode	Meaning
ref	Read/write reference
refin	Read-only input reference
refout	Output reference
refnull	Nullable reference

function SetValue(value : ref int):
    value = 5
endfunc

function SumInput(value : refin int) -> int:
    return value + 1
endfunc

function MakeValue(value : refout int):
    value = 33
endfunc

function MaybeSet(value : refnull int):
    if %value == null:
        return
    endif
    value = 44
endfunc

refnull accepts null as an argument. Inside the function, %param == null tests whether a real storage location was supplied.

Default Arguments

Parameters may have default values.

function Repeat(text : strview, count : int = 1):
    // ...
endfunc

Default arguments are used when the caller omits the trailing argument.

Variable Arguments

External functions can declare C-style variable arguments with ....

function printf(fmt : ^char, ...) -> int  [[external]]

DQ library functions commonly use []anyvalue for type-checked variable value lists.

Print("{} {}", ["value", 123])

Function Overloading

Overloaded functions and methods must be marked with [[overload]].

function Print(value : int) [[overload]]:
    // ...
endfunc

function Print(value : strview) [[overload]]:
    // ...
endfunc

The overload set is selected by argument types.

Function References

Function reference types are declared with type.

type FUnary = function(value : int) -> int

function Inc(value : int) -> int:
    return value + 1
endfunc

var cb : FUnary = Inc
var value : int = cb(10)

Function references may be null and can be compared with null.

A typed or opaque pointer can be explicitly cast to a plain function reference for low-level interoperability, such as constructing an interrupt vector table. The pointer does not carry signature information, so the declared function reference signature determines how an indirect call is generated.

type FHandler = function()
var raw : pointer = GetHandlerAddress()
var handler : FHandler = FHandler(raw)

This conversion is never implicit and is not available for object method reference types declared with of object.

if cb <> null:
    cb(1)
endif

Object method references add of object.

type FObjText = function(msg : cstring) of object

Special Functions

Names beginning with * are special-purpose functions.

*Main is the program entry point.

function *Main() -> int:
    return 0
endfunc

*ModuleInit is a module initialization function, called before the *Main()

var g_handler : OHandler = null

function *ModuleInit():
    g_handler = new OHandler()
endfunc

On bare-metal targets, the application owns its entry point and must call the compiler-generated dq_module_init() after initialized data and zeroed storage are ready. This runs the initialization functions of all used DQ modules, including generated constructors for global fixed objects.

*Create is an object constructor and *Destroy is an object destructor.

object OThing:
    function *Create(value : int):
        // ...
    endfunc

    function *Destroy():
        // ...
    endfunc
endobj