[no subject]

[RMS@MIT-AI]

This is relevant because of ITER, which uses DISPLACE but can't
supply one since that would clobber the user's own displace in
an execution environment.  But this means that the user of ITER must
make sure himself that there is a DISPLACE present in the compiler
when he compiles anything that uses ITER.

If the compiler had its own displace, a user could win just by
putting his favorite displace in his .lisp. (init).  Then
during execution he would have his own style of displace,
whereas during compilation he would have the compiler's appropriate one.
As it is now, he must not only have a displace in his lisp init
for execution time, but a (declare (defun displace (old new) new))
in the front of every file for compile time.