; different ways to navigate trees

(def tree (x)

(annotate 'tree x))

(defextend walk (seq f) (isa seq 'tree)

(let x rep.seq

(f x)

(when (acons x)

(walk (tree car.x) f)

(walk (tree cdr.x) f))))

(defextend map (f seq) (isa seq 'tree)

(withs (old rep.seq

new f.old)

(if (or (~acons old) (~is old new))

new

(cons (map f (tree car.old))

(map f (tree cdr.old))))))

(def leaves (x)

(annotate 'leaves x))

(defextend walk (seq f) (isa seq 'leaves)

(let x rep.seq

(if (~acons x)

(f x)

(do (walk (leaves car.x) f)

(walk (leaves cdr.x) f)))))

(defextend reduce (f base seq) (isa seq 'leaves)

(let x rep.seq

(if (~acons x)

base

(f (reduce f base (leaves car.x))

(reduce f base (leaves cdr.x))))))

(defextend counts (seq) (isa seq 'leaves)

(counts:flat rep.seq))