That's the usual late-binding semantics for global functions in Lisp. Note that in Common Lisp a compiler can assume that the recursive call is actually the sa

That's the usual late-binding semantics for global functions in Lisp. Note that in Common Lisp a compiler can assume that the recursive call is actually the same function: > Within a function named F, the compiler may (but is not required to) assume that an apparent recursive call to a function named F refers to the same definition of F, unless that function has been declared notinline. The consequences of redefining such a recursively defined function F while it is executing are undefined.