; uLisp Animals Game v3 - 8th June 2021
; see http://www.ulisp.com/show?1LKX
;

(defvar *data* '("Does it live in the sea?" "a dolphin" "a horse"))

(defun yes-no ()
  (eq (read) 'y))

(defun add (animal new)
  (format t "~%Give me a yes/no question to distinguish between ~a and ~a: " new animal)
  (let ((question (read-line)))
    (format t "~%What would the answer be for ~a ? " new)
    (if (yes-no)
        (list question new animal)
      (list question animal new))))

(defun try (animal)
  (format t "~%Is it ~a ?" animal)
  (cond
   ((yes-no) (format t "~%Ho ho!") animal)
   (t (format t "~%What were you thinking of? ")
      (add animal (read-line)))))

(defun ask (tree)
  (format t "~%~a " (first tree))
  (if (yes-no)
      (list (first tree) (run (second tree)) (third tree))
    (list (first tree) (second tree) (run (third tree)))))

(defun run (tree)
  (if (listp tree)
      (ask tree)
    (try tree)))

(defun go ()
  (setq *data* (run *data*))
  nil)