FUNCTION func-spec

The FUNCTION keyword provides the reference to the specified function.


FUNCTION [module-name.]function-name
  1. module-name is the name of an imported module.
  2. function-name is the name of a function defining in the current module or in an imported module.


Inside a MAIN or FUNCTION block, the FUNCTION keyword instructs the compiler to use the next symbol as the name of a function, rather than the name of a variable (the language allows the declaration of variables and functions with the same name in the same module).

The function specification following the FUNCTION keyword can be a single function name or a function name prefixed by a module name.

Note: The return-types of the referenced functions must be known: If the referenced function returns one or more values, the function type and the function itself must be defined with a RETURNS clause. Otherwise, the compiler will produce the error -8419.

A FUNCTION func-spec expression is typically used to assign a variable defined with a TYPE referencing a function. It can also be used as parameter in a function call, but it cannot be combined with other expressions.

Important: In order to assign a function reference to a variable, the variable must have been defined with a function type that matches the referenced function: The function parameter names and types, as well as the return types must be the same. If the signatures of the function type and function reference do not match, the compiler produces the error -6631.


IMPORT FGL mymodule

TYPE callback_function FUNCTION(p1 INT, p2 INT) RETURNS INT

    RETURN p1 + p2

    DEFINE v callback_function
    LET v = FUNCTION add  -- Assign function reference to the variable
    CALL process( FUNCTION add, ... ) -- Function reference passed as parameter
    LET v = FUNCTION mymodule.sub  -- Using a module prefix