; BINARY TREE STUFF ; Tree constructors: (define (make-tree left-tree root-node right-tree) (list left-tree root-node right-tree)) (define (leaf root-node) (make-tree '() root-node '())) ; Tree accessors: (define root cadr) (define left-tree car) (define right-tree caddr) ; Tree predicates: (define inner-node? pair?) (define leaf? number?) (define empty-tree? null?) ; Two concrete trees - identical to the ones shown on the previous slide: (define tr1 (make-tree (make-tree (leaf 2) 4 (leaf 3)) 7 (make-tree (make-tree '() 0 (leaf 9)) 1 (leaf 5)))) (define tr2 (make-tree (make-tree (make-tree '() 1 (leaf 9)) 0 (leaf 7)) 8 (make-tree (make-tree (leaf 2) 7 '()) 6 (leaf 1))))