Functions are declared using the FUNCTION keyword:

FUNCTION square(x: Number): Number
    RETURN x ^ 2

The return type of a function (appearing after the )) is optional. The RETURN statement is not permitted inside a function that does not return a value (use EXIT FUNCTION instead).

Parameter Modes

Function parameters may be declared with a parameter mode:

  • IN - The function parameter is passed from the caller into the function, and may not be modified within the function.

  • INOUT - A reference to the function argument is passed to the function, and the parameter may be modified within the function.

  • OUT - No value is passed into the function, but any value assigned within the function is passed back to the caller.

The default parameter mode is IN. For INOUT and OUT parameters, the caller must supply an actual variable rather than the result of an expression.

When calling a function with a parameter that has INOUT or OUT modes, the parameter mode must also be declared in the call:

FUNCTION double(INOUT x: Number)
    x := x * 2

VAR a: Number := 5
double(INOUT a)

Default Parameter Value

Function parameters may be declared with a default value.


FUNCTION add(INOUT x: Number, delta: Number DEFAULT 1)
    x := x + delta

VAR value: Number := 5
add(INOUT value)
add(INOUT value, 2)

When a parameter is not specified and it has a default value, the function call is executed as if the parameter were present and had the given value. Default parameter values only apply to IN mode parameters.

Named Parameters

When calling a function, function parameters may be named using the WITH keyword.


FUNCTION birthdayParty(name: String, balloons: Number, cake: String, clown: Boolean)
    -- ...

birthdayParty(name WITH "Helen", balloons WITH 10, cake WITH "Chocolate", clown WITH TRUE)

Parameters may be passed in order without using WITH, and then switch to using WITH for the remainder of the function call. Each non-default parameter must be specified exactly once in the function call.