Common Lisp seems to go to great lengths to provide both nondestructive functions (like subst & remove) and destructive functions and modify macros (like delete & rotatef) for general use. Presumably this is to effectively support both functional and nonfunctional styles of programming. But there also seems to be a particular bias toward the nonfunctional style in the design of the ubiquitous `setf`. The `setf` macro, incorporating generalized reference, is apparently flexible enough to modify any specifiable place (except perhaps for immutable integers and characters). This power probably accounts for its widespread useage in spite of its nonfunctional/destructive behavior.

The question is why there is not a corresponding "functional style" nondestructive operator, patterned after `setf` (call it put, since `set` is already taken), analogous to other nondestructive/destructive lisp operator pairs. Such an operator would probably take the same arguments, a place and a value, but would return a copy of the object in which the place was embedded, instead of the new value at that place. It also would probably involve a universal copier of some sort, with the standard `setf` simply modifying the copy before returning it. The nondestructive operator then could be used in lieu of `setf` for most assignments, with `setf` being reserved for really large objects. Is such an operator feasible (or even possible) given the (presumed) requirement for a universal copier and the need to recover an object from an arbitrary place embedded in it?