On Oct 29, 2018, at 10:52 AM, Steve Johnson <scj@yaccman.com> wrote:

We actually had a pretty good system for making changes like that.  First, we would change
the compiler to accept both the old and the new.   Then we would produce a warning
that on a particular date the old would no longer work.  Then we made the old an error
and printed a message about how to fix it.   Eventually, we just let it be a syntax error.
This process was applied many times on the way from typeless B to strongly typed C.

Was there ever a time when a change was desired that you couldn’t accept both
the old and the new?