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A function is a named "black box" that returns a value. The user interacts with the function through the function’s parameters, and possibly through global variables (Global Variables).
LUX offers many built-in functions (Internal Routines), and also allows you to define your own in the LUX language, with a function definition statement.
FUNC name [ , par1, par2, … ] statement1 [ statement2 … ] ENDFUNC
This defines a function called name, with parameters
par1, par2, etcetera. The function consists
of the statements statement1, statement2,
etcetera, which use the parameters to determine what needs to be done.
A function must return a value, and to this end at least one
return statement must appear in each function definition. A
return statement in a function definition looks like this:
RETURN, value
The value value is what the function call returns. See
Function Call for the use of a function.
A special method is available for allowing arbitrary numbers of
variables. It is selected by adding a triple period (...) as the
last parameter of the subroutine, and then if any arguments fall beyond
the last regular one, then the last regular parameter is changed into a
cplist variable and its previous value and all subsequent ones
are entered into the list in the order in which they are specified.
See Extended Parameter Lists for more details.