protocol ¶(protocol traversal ...)
or
(any traversal ...)
Try executing traversals, in order, until one succeeds (and then stop).
"Try going forward, if that doesn’t work try going backward."
(symex-eval
(symex-traversal
(any (move forward)
(move backward))))
"Try going forward and up, if that doesn’t work try going backward and down."
(symex-eval
(symex-traversal
(any (do (move forward)
(move up))
(do (move backward)
(move down)))))