"A reference to a function. The type arguments encode the function return type and parameter types. The parameter types are typically represented as a tuple type. For example, the type of the function reference `plus<Float>` is: Callable<Float,[Float,Float]> which we usually abbreviate `Float(Float,Float)`. Any instance of `Callable` may be _invoked_ by supplying a positional argument list: Float(Float,Float) add = plus<Float>; value four = add(2.0, 2.0); or by supplying a tuple containing the arguments: Float(Float,Float) add = plus<Float>; [Float,Float] twoAndTwo = [2.0, 2.0]; value four = add(*twoAndTwo); This interface may not be implemented by user code." see (`class Tuple`) shared interface Callable<out Return, in Arguments> given Arguments satisfies Anything[] {}