"SICP Exercise" 93 Exercise 2.66

Exercise 2.66

This problem is equivalent to two fork tree in the actual project of one application, we still need to use the previous three processes learned: entry, Left-branch, Right-branch. The three functions are taking out the node, the left branch and the right branch. And according to the topic request, here also need a key that gets the value. Of course, as shown in the book above, key does not need to be written out, and here is a desire to think.

(Define (lookup given-key tree-of-records)   (if (null? tree-of-records)#f( Let (entry-key ( key (entry tree-of-records )))         (Cond ((= given-key entry-key) (entry tree-of-records))               (> given-key entry-key) (lookup given-key (right-branch tree-of-records )))                (< given-key entry-key) (lookup given-key (left-branch Tree-of-records )))))))

"SICP Exercise" 93 Exercise 2.66