FuncStream is one of the most basic ways to describe a stream: it has a function that is called for each next stream value.
It uses Function: -inEnvir to statically bind the function call to the environment in which the
FuncStream was created.
Return a new stream object.
The function that is called on each next
The function that is called on reset
Return the next value by calling the function.
Call the reset function, if defined.
Get or set the environment to which the function has been bound.
Get or set the function which is called on -next.
Get or set the function which is called on -reset.