main.cpp

包括图、二叉树、链表

#include "stack.h"
#include <iostream>
using namespace std;
void introduction()
/*
PRE: None.
POST: An introduction to the program Polynomial Calculator is printed.
*/
{
	cout << "Polynomial Calculator Program." << endl
		<< "This program simulates a polynomial calculator that works on a\n"
		<< "stack and a list of operations. It models a reverse Polish\n"
		<< "calculator where operands are entered before the operators. An\n"
		<< "example to add two polynomials and print the answer is ?P?Q+= .\n"
		<< "P and Q are the operands to be entered, + is add, and = is\n"
		<< "print result. The result is put onto the calculator's stack.\n\n";
}
void instructions()
/*
PRE: None.
POST: Prints out the instructions and the operations allowed on the
calculator.
*/
{
	cout << "\nEnter a string of instructions in reverse Polish form.\n"
		<< "The allowable instructions are:\n\n"
		
		<< " ?:Read   +:Add =:Print   -:Subtract\n "	
		<< " q:Quit   h:Help\n\n                   "
		<<endl;
		
}


  
char get_command()

  /*
  PRE: None.
  POST: A legal command is read from the user and returned.
  */
{
	char command, d;
	cout << "Select command and press <Enter>:";
	while (1) {
		do {
			cin.get(command);
		} while (command == '\n');
		do {
			cin.get(d);
		} while (d != '\n');
		command = tolower(command);
		if (command == '?' || command == '=' || command == '+' ||
			command == '-' || command == 'h' || command == '*' ||
			command == '/' || command == 'q' || command == 'p' ||
			command == 'h') {
			return (command);
		}
		cout << "Please enter a valid command:" << endl;
		instructions();
	}
}
bool do_command(char command, Stack &stored_polynomials)
/*
Pre: The first parameter specifies a valid
calculator command.
Post: The command specified by the first parameter
has been applied to the Stack of Polynomial
objects given by the second parameter.
A result of true is returned unless
command == 'q'.
Uses: The classes Stack and Polynomial.
*/

{
	Polynomial p, q, r;
	switch (command) {
	case '?':
		p.read();
		if (stored_polynomials.push(p) == overflow)
			cout << "Warning: Stack full, lost polynomial" << endl;
		break;
		
	case '=':
		if (stored_polynomials.empty())
			cout << "Stack empty" << endl;
		else {
			stored_polynomials.top(p);
			p.print();
		}
		break;
		
	case '+':
		if (stored_polynomials.empty())
			cout << "Stack empty" << endl;
		else {
			stored_polynomials.top(p);
			stored_polynomials.pop();
			if (stored_polynomials.empty()) {
				cout << "Stack has just one polynomial" << endl;
				stored_polynomials.push(p);
			}
			
			else {
				stored_polynomials.top(q);
				stored_polynomials.pop();
				r.equals_sum(q, p);
				if (stored_polynomials.push(r) == overflow)
					cout << "Warning: Stack full, lost polynomial" << endl;
			}
		}
		break;
		
		//	Add options for further user commands.
	case '-':
		if (stored_polynomials.empty()) cout << "Stack empty" << endl;
		else {
			stored_polynomials.top(p);
			stored_polynomials.pop();
			if (stored_polynomials.empty()) {
				cout << "Stack has just one polynomial" << endl;
				stored_polynomials.push(p);
			}
			else {
				stored_polynomials.top(q);
				stored_polynomials.pop();
				r.equals_difference(q, p);
				if (stored_polynomials.push(r) == overflow)
					cout << "Warning: Stack full, lost polynomial" << endl;
			}
		}
		break;
	case 'h':
		instructions();
		break;
	case 'q':
		cout << "Calculation finished." << endl;
		return false;
	}
	return true;
}
void main()
/*
The program has executed simple polynomial arithmetic
commands entered by the user.
Uses: The classes Stack and Polynomial and the functions
introduction, instructions, do_command, and
get_command.
*/
{
	Stack stored_polynomials;
	introduction();
	instructions();
	while (do_command(get_command(), stored_polynomials));

}