As of 4D v19 R3, the 4D language is more flexible when the code accesses parameters declared but not passed.
For example, the following code no longer provokes an error:

// "concat" function of myClass Function concat ($param1 : Text ; $param2 : Text) Alert($param1+" "+$param2)

//calling method $class:=cs.myClass.new() $class.concat("Hello";"world") // displays "Hello world" $class.concat("Hello") // displays "Hello" $class.concat() // displays " "

Note:
To benefit from this, you must recompile both calling and called methods; thus components must be recompiled.