See: http://mathworld.wolfram.com/Combinator.html
     http://www.ece.uc.edu/~franco/C511/html/Scheme/ycomb.html

In mathematical terms, "a generalized function whose argument is also a
function".

Divmod Combinator's purpose is to provide Python developers with a development
environment by performing common manipulations upon a body of code.  It is
named after a combinator because both its input and output are code.

Because of the popularity of the Y-combinator, it is conventional to title the
Windows drive letter where you keep code managed by Combinator "Y:".