Redefinition of Common Lisp Functions

["Scott E. Fahlman" <Fahlman@C.CS.CMU.EDU>]

    Attempts to directly redefine
    the functions may cause an error to be signalled.
    This technique would require no changes in the standard, or
    the standard could be toughened up to require that an error
    be signalled, as long as it is not toughened to the point
    where shadowing Common Lisp functions is an error.

Unless I missed something, nobody is proposing that SHADOWING a built-in
function using the package system should signal an error or should "be
an error".  That's what the package system is for.

Clobbering the definitions of built-in symbols in the Lisp package is
another matter.  I think there's pretty general agreement that this
should be an "is an error situation", and that it would be tasteful to
at least issue a warning in such cases, perhaps under control of a magic
implementation-dependent switch.

-- Scott