An Arc-like sketch of an s-expression Esterel.

gistfile1.arc

http://en.wikipedia.org/wiki/Esterel

(nothing)
(pause)
(do p q ...)
(par p q ...)
(forever p)
(let s p)
(emit s)
(ifelse s p q)
(suspend-if s p)
(catch trap p)
(throw trap)

(esterel-mac halt ()
  '(forever:pause))

(esterel-mac sustain (x)
  `(forever:do (emit s) (pause)))

(esterel-mac if body
  (iflet (first . rest) body
    (iflet (then . rest) rest
      `(ifelse ,first ,then (if ,@rest))
      first)
    '(nothing)))

(esterel-mac await (s)
  (w/uniq trap
    `(catch ,trap (forever:do (pause) (if ,s (throw ,trap))))))

(esterel-mac await-immediate (s)
  (w/uniq trap
    `(catch ,trap (forever:do (if ,s (throw ,trap)) (pause)))))

(esterel-mac suspend-if-immediate (s p)
  `(suspend-if ,s (do (if ,s (pause)) ,p)))

(esterel-mac abortpar body
  (w/uniq trap
    `(catch ,trap (par ,@(map [do `(do ,_ (exit ,trap))] body)))))

(esterel-mac weak-abort-if (s p)
  `(abortpar ,p (await ,s)))

(esterel-mac weak-abort-if-immediate (s p)
  `(abortpar ,p (await-immediate ,s)))

(esterel-mac abort-if (s p)
  `(weak-abort-if ,s (suspend-if ,s ,p)))

(esterel-mac abort-if-immediate (s p)
  `(weak-abort-if-immediate ,s (suspend-if ,s ,p)))

(esterel-mac do-while (s p)
  `(forever:abort ,s (do ,p (halt))))

(esterel-mac while (s p)
  `(do (await ,s) (do-while ,s ,p)))