Write a lookup predicate that looks up a value in a binary search tree like the kind defined in example 7.10.
As mentioned earlier in the text, Prolog originated out of Colmerauer’s interest in using logic to express grammar rules and to formalize the parsing of natural language sentences. Kowalski and Comerauer solved this problem together and Colmerauer figured out how to encode the grammar as predicates so sentences could be parsed efficiently. The next sections describe the implementation of parsing Colmerauer devised in 1972.
Consider implementing a lookup predicate for a binary search tree in Prolog. A tree may be defined recursively as either nil or a btnode(Val,Left,Right) where Val is the value stored at the node and Left and Right represent the left and right binary search trees. The recursive definition of a binary search tree says that all values in the left subtree must be less than Val and all values in the right subtree must be greater than Val. For this example, let’s assume that binary search trees don’t have duplicate values stored in them. A typical binary search tree structure might look something like this:
which corresponds to the tree shown graphically here.
Items may be inserted into and deleted from a binary search tree. Since Prolog programmers write predicates, the code to insert into and delete from a binary search tree must reflect the before and after picture. Because a binary search tree is recursively defined, each part of the definition will be part of a corresponding case for the insert and delete predicates. So, inserting into a search tree involves the value to insert, the tree before it was inserted, and the tree after it was inserted. Similarly, a delete predicate involves the same three arguments. Looking up a value in a binary search tree results in a true or false response, which is the definition of a predicate. Writing a lookup predicate requires the value and the search tree in which to look for the value.
Delivering a high-quality product at a reasonable price is not enough anymore.
That’s why we have developed 5 beneficial guarantees that will make your experience with our service enjoyable, easy, and safe.
You have to be 100% sure of the quality of your product to give a money-back guarantee. This describes us perfectly. Make sure that this guarantee is totally transparent.Read more
Each paper is composed from scratch, according to your instructions. It is then checked by our plagiarism-detection software. There is no gap where plagiarism could squeeze in.Read more
Thanks to our free revisions, there is no way for you to be unsatisfied. We will work on your paper until you are completely happy with the result.Read more
Your email is safe, as we store it according to international data protection rules. Your bank details are secure, as we use only reliable payment systems.Read more
By sending us your money, you buy the service we provide. Check out our terms and conditions if you prefer business talks to be laid out in official language.Read more