[R6RS] proposed generalizations of equal?

[William D Clinger]

For the record, let me clarify something I just wrote:
> > Does this imply an opinion on =, char=?, char-ci=?, string=?, and
> > string-ci=?
>
> Yes, it implies my opinion.  All of those are total orders,

A total order consists of a set and a binary relation.
The following are total orders:

    the reals ordered by <=

    the characters ordered by char<=?

    the equivalence classes of characters modulo char-ci=?
    ordered by char-ci<=?

    the strings ordered by string<=?

    the equivalence classes of strings modulo string-ci=?
    ordered by string-ci<=?

In the reals ordered by <=, the equality predicate is =.
Hence my general rule would have = take two or more arguments,
even though = also serves as the equality predicate on complex
numbers, which are not totally ordered.

In the characters and strings ordered by case-insensitive
operations, individual characters and strings serve as
representatives of the equivalence classes.  Hence my
general rule would have char-ci=? and string-ci=? take
two or more arguments, even though the characters are
not totally ordered by char-ci<=? and the strings are
not totally ordered by string-ci<=?.

Will