(setf (compiler-macro-function name &optional environment) new-function)
name—a function name.
environment—an environment object.
function, new-function—a compiler macro function, or nil.
Accesses the compiler macro function named name, if any, in the environment.
A value of nil denotes the absence of a compiler macro function named name.
The consequences are undefined if environment is non-nil
in a use of setf of compiler-macro-function.