Simple combinators working solely on and with functions.
takes its (first) two arguments in the reverse order of
Application operator. This operator is redundant, since ordinary
(f x) means the same as
(f . However,
low, right-associative binding precedence, so it sometimes allows
parentheses to be omitted; for example:
f $ g $ h x = f (g (h x))
is the least fixed point of the function
i.e. the least defined
x such that
f x = x.