[r6rs-discuss] Comparison procedures' number of arguments

[Abdulaziz Ghuloum]

On Oct 21, 2008, at 8:03 AM, Ken Dickey wrote:

> Doesn't it make more sense to require existence for comparison?

Existence of one ordered pair does not matter much.  You need
to either prove the existence of a counter example to produce
#f, or to prove universality (e.g., with for-all) to produce #t.

You can't say: I'll require that all adjacent pairs are ordered,
except when there are no pairs, where I'll switch my logic and
demand the existence of an ordered pair.

> (define (monotonic? ordered? sequence)
>   (let ( [list-of-pairs (pairs-in sequence)] )
>     (if (null? list-of-pairs)
>         #f
>         (for-all
>          (lambda (pair) (ordered? (car pair) (cdr pair)))
>          list-of-pairs))
> ) )


You just made an arbitrary exception to the rule by providing
an arbitrary value for the (null? ---) case.  I don't see that
following your rule of least surprise.

Aziz,,,