syntax-rules: coalesce

これの関連で。。

• vallog: syntax-rules: if-true

こういうのが

(let1 e 'd
  (if (or (if (eq? e 'a)
              'car)
          (if (eq? e 'd)
              'cdr))
      'found
      'notfound))

こうなる

(let1 e 'd
  (if (coalesce ((eq? e 'a) 'car)
                ((eq? e 'd) 'cdr))
      'found
      'notfound))

cond みたい。inspired by SQL's coalesce.