On Wed, Mar 4, 2020 at 9:48 AM Jim Rees <xxxxxx@gmail.com> wrote:

If we are to honor R7RS, with u8-ready? and char-ready?  I think we are obligated to support their implementation in custom ports as well, otherwise, we are declaring those procedures deprecated and useless (which may be a valid decision).

Third option - perhaps the simplest - just declare the result of {u8,char}-ready? on custom ports to be unspecified.   This effectively makes them portably useless w.r.t. custom ports, but doesn't prohibit an implementation from doing better.