Overview of Procedure Pointers and Function Values

Quxlang has two ways to pass callable behavior: a procedure pointer is a runtime address with a fixed signature, while a function value preserves the identity of a selected Quxlang function during generic compilation.

Runtime procedure pointers

::is_positive FUNCTION(@value I32): BOOL
{
  RETURN value > 0;
}

VAR predicate CONST->PROCEDURE(@value I32: BOOL) := is_positive<-;
VAR accepted BOOL := predicate(@value 4);

The PROCEDURE type records parameter types, API names, and the result type. A procedure pointer represents callbacks and ABI boundaries that require a runtime function address.

VAR native_callback CONST->PROCEDURE CCALL NOEXCEPT(I32: I32);

Calling-convention and NOEXCEPT qualifiers are part of that runtime type.

Compile-time function values

::invoke FUNCTION(@callable AUTO(fn), @value I32): BOOL
{
  RETURN callable(@value value);
}

VAR accepted BOOL := invoke(@callable is_positive, @value 4);

AUTO(fn) binds the chosen callable without first erasing it to a runtime address. This also works for a bound member such as object.method, which retains its receiver.

A function value supports generic composition, while a procedure pointer supports a fixed runtime representation. A bound member does not currently convert to a procedure pointer because that type has no captured-receiver slot.

Reference

See the Procedure Pointers and Function Values Reference for named and positional signatures, qualifiers, deduction compatibility, and conversion limitations.