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// FILE: animal.cxx
// An animal-guessing program to illustrate the use of the binary tree toolkit.
#include <cstdlib> // Provides EXIT_SUCCESS
#include <iostream> // Provides cout
#include <string> // Provides string class
#include "bintree.h" // Provides the binary tree node functions
#include "useful.h" // Provides eat_line, inquire (from Appendix I)
using namespace std;
using namespace main_savitch_10;
// PROTOTYPES for functions used by this game program:
void ask_and_move(binary_tree_node<string>*& current_ptr);
// Precondition: current_ptr points to a non-leaf node in a binary taxonomy tree.
// Postcondition: The question at the current node has been asked. The current
// pointer has been shifted left (if the user answered yes) or right
// (for a no answer).
binary_tree_node<string>* beginning_tree( );
// Postcondition: The function has created a small taxonomy tree. The return
// value is the root pointer of the new tree.
void instruct( );
// Postcondition: Instructions for playing the game have been printed to the
// screen.
void learn(binary_tree_node<string>*& leaf_ptr);
// Precondition: leaf_ptr is a pointer to a leaf in a taxonomy tree. The leaf
// contains a wrong guess that was just made.
// Postcondition: Information has been elicited from the user, and the tree has
// been improved.
void play(binary_tree_node<string>* current_ptr);
// Precondition: current_ptr points to the root of a binary taxonomy tree with
// at least two leaves.
// Postcondition: One round of the animal game has been played, and maybe the
// tree has been improved.
int main( )
{
binary_tree_node<string> *taxonomy_root_ptr;
instruct( );
taxonomy_root_ptr = beginning_tree( );
do
play(taxonomy_root_ptr);
while (inquire("Shall we play again?"));
cout << "Thank you for teaching me a thing or two." << endl;
return EXIT_SUCCESS;
}
void ask_and_move(binary_tree_node<string>*& current_ptr)
// Library facilities used: bintree.h, string, useful.h
{
cout << current_ptr->data( );
if (inquire(" Please answer:"))
current_ptr = current_ptr->left( );
else
current_ptr = current_ptr->right( );
}
binary_tree_node<string>* beginning_tree( )
// Library facilities used: bintree.h, string
{
binary_tree_node<string> *root_ptr;
binary_tree_node<string> *child_ptr;
const string root_question("Are you a mammal?");
const string left_question("Are you bigger than a cat?");
const string right_question("Do you live underwater?");
const string animal1("Kangaroo");
const string animal2("Mouse");
const string animal3("Trout");
const string animal4("Robin");
// Create the root node with the question “Are you a mammal?”
root_ptr = new binary_tree_node<string>(root_question);
// Create and attach the left subtree.
child_ptr = new binary_tree_node<string>(left_question);
child_ptr->set_left( new binary_tree_node<string>(animal1) );
child_ptr->set_right( new binary_tree_node<string>(animal2) );
root_ptr->set_left(child_ptr);
// Create and attach the right subtree.
child_ptr = new binary_tree_node<string>(right_question);
child_ptr->set_left( new binary_tree_node<string>(animal3) );
child_ptr->set_right( new binary_tree_node<string>(animal4) );
root_ptr->set_right(child_ptr);
return root_ptr;
}
void instruct( )
// Library facilities used: iostream
{
cout << "Let's play!" << endl;
cout << "You pretend to be an animal, and I try to guess what you are.\n";
}
void learn(binary_tree_node<string>*& leaf_ptr)
// Library facilities used: bintree.h, iostream, string, useful.h
{
string guess_animal; // The animal that was just guessed
string correct_animal; // The animal that the user was thinking of
string new_question; // A question to distinguish the two animals
// Set strings for the guessed animal, correct animal and a new question.
guess_animal = leaf_ptr->data( );
cout << "I give up. What are you? " << endl;
getline(cin, correct_animal);
cout << "Please type a yes/no question that will distinguish a" << endl;
cout << correct_animal << " from a " << guess_animal << "." << endl;
cout << "Your question: " << endl;
getline(cin, new_question);
// Put the new question in the current node, and add two new children.
leaf_ptr->set_data(new_question);
cout << "As a " << correct_animal << ", " << new_question << endl;
if (inquire("Please answer"))
{
leaf_ptr->set_left( new binary_tree_node<string> (correct_animal) );
leaf_ptr->set_right( new binary_tree_node<string> (guess_animal) );
}
else
{
leaf_ptr->set_left( new binary_tree_node<string> (guess_animal) );
leaf_ptr->set_right( new binary_tree_node<string> (correct_animal) );
}
}
void play(binary_tree_node<string>* current_ptr)
// Library facilities used: bintree.h, iostream, string, useful.h
{
cout << "Think of an animal, then press the return key.";
eat_line( );
while (!current_ptr->is_leaf( ))
ask_and_move(current_ptr);
cout << ("My guess is " + current_ptr->data( ) + ". ");
if (!inquire("Am I right?"))
learn(current_ptr);
else
cout << "I knew it all along!" << endl;
}
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