Functions

This page defines function declarations, parameters, overloads, and special functions. See the Functions guide for common usage.

Declaration and Definition

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

A signature consists of the function name, ordered parameter types and modes, return type, calling convention, object binding, and relevant attributes. A declaration without a body can be implemented later with the same signature.

Result Values

A function without -> has no result value. A value-returning function can return an expression directly or assign the built-in result variable. Every reachable normal exit must leave a valid result.

Parameter Modes

Plain parameters are passed by value. Reference modes alias caller storage:

Mode	Contract
name : T	function receives a value
name : ref T	readable and writable alias
name : refin T	readable alias, not writable through the parameter
name : refout T	writable output alias; input value is not part of the contract
name : refnull T	nullable reference; accepts null

The argument must be an addressable, lifetime-compatible value for a reference parameter. Passing a reference never transfers ownership unless a specific API documents a separate ownership convention.

View types such as []T, strview, and cstring borrow their underlying storage even when the descriptor itself is passed by value.

Default and Named Arguments

A default expression supplies an omitted trailing argument. Named arguments use the declared parameter name and participate in overload selection.

function Open(path : strview, retries : int = 0)
Open(path = "data.txt", retries = 2)

Defaults must be valid where declared and do not create additional runtime overloads.

Overloading

Functions explicitly marked for overloading may share a name when their signatures can be distinguished. Resolution considers argument count, names, parameter modes, and defined conversion costs. An ambiguous best match is a compile error.

Return type alone does not distinguish overloads.

Variadic Functions

C-compatible variadic external functions use ... and follow the target C ABI, including its default argument promotions. DQ-native heterogeneous interfaces normally use an []anyvalue parameter and contextual array literals.

The caller and declaration author are responsible for external variadic type agreement; the callee has no DQ signature information for the unnamed values.

Function References

Functions can be assigned to a compatible function(...) reference type. Object methods require an of object reference. See Structures, Pointers, and Function References.

Attributes and External Functions

Attributes control behavior such as external, overload, inline, weak, and object virtual dispatch. Attributes cannot be combined when their execution models conflict. See Attributes, Directives, and Interoperability.

Special Functions

Special names beginning with * define compiler/runtime entry points such as constructors, destructors, module initialization, and the program main function. Their permitted signature and placement depend on the specific special name; they are not ordinary callable overload names.