Am So., 28. Juni 2020 um 23:08 Uhr schrieb Shiro Kawai <xxxxxx@gmail.com>:
>
> On Sun, Jun 28, 2020 at 11:01 AM Marc Nieper-Wißkirchen <xxxxxx@nieper-wisskirchen.de> wrote:
>>
>>
>> While this syntax is possible, it is not a natural extension to the
>> syntax of case, I think, because the R7RS version case already quotes
>> without any explicit (quasi)quote.
>
>
> I'd argue that '(a ,x) and `(a ,x) are quite different, so explicit quasiquote would help.
> And if you employ equal? instead of eqv?, wouldn't you expect (case ',x ((a ,x) #t) (else #f)) returns #t?

I have to admit that `case' is not the best example because one would
want to change the semantics from `eqv?' to `equal?' as well.

A better, real-life example is SRFI 159. The state variables there are
symbols (as opposed to the "corrected" version SRFI 166). One syntax
is

(with ((a ...)) ...)

which binds the state variable `a'. While initially experimenting with
SRFI 159, I had extended the syntax to allow gensyms (to get some kind
of hygiene for state vars), and the most natural extension was (at
least for me):

(define x (gensym))

(with ((,x ...)) ...)

Marc