#include <cstdlib>
#include <iostream>
#include <fstream>
#include <stack>
#include <string>
#include <queue>
#include <stdio.h>
#include <ctype.h>
#include <cstring>
 
using namespace std;
 
queue<char> INFIX_TO_POSTFIX(ifstream &);
void EVALUATE_POSTFIX(queue<char> &);
int precedence(char);
 
int main()
{
    ifstream inFile;
    inFile.open("a2.txt"); //attempts to open read file, and tests for existance
    if(inFile.is_open())
           cout << "File Exists." << endl << endl;
    else
           cout << "File does not exist." << endl << endl;
 
    queue<char> bigqueue;
 
    //while(!inFile.eof())
  //  {       
        bigqueue = INFIX_TO_POSTFIX(inFile);   //Function call
//    }
        EVALUATE_POSTFIX(bigqueue);
 
 //   float tool = 7 + (4 - 6) * (8 + 6) / 3;
  //  cout << endl << tool << endl;
 
    system("PAUSE");
    return EXIT_SUCCESS;
}
 
queue<char> INFIX_TO_POSTFIX(ifstream &Filein) //function, Filein is just the name of my text file read stream
{
 
    stack<char> thestack;
    queue<char> thequeue;
 
    string data;  //string created to store the input read line
    getline(Filein, data);    //program reads file, stores read line as the string, data
    cout << "The original infix expression is: " << data << endl; //output read string
    char dataarray[25] = {0}; //char array created
    int arrayLength = data.length();  //set a counter
    char temp;    //temporary variable
 
    for(int i = 0; i < arrayLength; i++) //for loop set up to step through the character array, one character at a time
    {
          dataarray[i] = data[i]; //Here's the key line, I equate each position in the string to equate to the character array
 
          if(isdigit(dataarray[i]))   //Here on out is where the processing of the character array begins....
              thequeue.push (dataarray[i]);//output content(Next) to Queue;
 
          else if(dataarray[i] == '(')
              thestack.push (dataarray[i]);
 
          else if(dataarray[i] == ')')
          {
              if(thestack.empty() == false)
              {
                  while(thestack.top() != '(')
                  {
                      temp = thestack.top();
                      thequeue.push(temp);
                      thestack.pop();
                      if(thestack.empty() == true)
                      {
                          break;
                      }                              //POP the content in Stack to Queue until “(“ is reached,
                  }
              }
              thestack.pop();                                             //POP it but not to Queue; break;
          }
 
          else if(dataarray[i] == '+' || '-' || '*' || '/' || '^')
          {
              if(thestack.empty() == false)
              {
                  while(precedence(thestack.top()) >= precedence(dataarray[i]))                      //while(PRE(TOP) >= PRE(Next))
                  {
                      temp = thestack.top();
                      thequeue.push(temp);
                      thestack.pop();
                      if(thestack.empty() == true)
                      {
                          break;
                      }
                  }
              }
              thestack.push(dataarray[i]);
          }
 
          else
              cout << "There was an error in the operation, please restart." << endl;
    }
 
    while(!thestack.empty())                                            //while(PRE(TOP) >= PRE(Next))
    {
          temp = thestack.top();
          thequeue.push(temp);
          thestack.pop();
    }
    return(thequeue);
}
 
int precedence(char thing)
{
    int compare;
    switch(thing)
    {
        case '^': compare = 3;
        break;
        case '/': 
        case '*': compare = 2;
        break;
        case '+':
        case '-': compare = 1;
        break;
        case '(':
        case ')': compare = 0;
        break;
    }
    return (compare);
}
 
void EVALUATE_POSTFIX(queue<char> &postqueue)
{
    stack<float> poststack;
    int queueLength;
    float final;
    char var, temp, temp1, temp2;
    queueLength = postqueue.size();
 
    for(int j = 0; j < queueLength; j++)
    {
        cout << postqueue.front();
        if(isdigit(postqueue.front()))
        {
            var = postqueue.front();
            poststack.push(var);
        }
 
        else if(postqueue.front() == '+' || '-' || '*' || '/' || '^')
        {
            temp2 = poststack.top();
            poststack.pop();
            temp1 = poststack.top();
            poststack.pop();
            switch(postqueue.front())
            {
                case '+': temp = temp1 + temp2;
                    break;
                case '-': temp = temp1 - temp2;
                    break;
                case '*': temp = temp1 * temp2;
                    break;
                case '/': temp = temp1 / temp2;
                    break;
                case '^': temp = temp1 ^ temp2;
                    break;
                default: cout << "There was a glitch in the operation, press any key to terminate.";
            }
            poststack.push(temp);
        }
        postqueue.pop();
    }
    final = poststack.top();
    cout << endl << "The postfix operation answer is: " << poststack.top() << endl;
    return;
}

void EVALUATE_POSTFIX(queue<char> &postqueue)
{
    stack<float> poststack;
    int queueLength;
    char var;
    float var1, temp, temp1, temp2, final;
    queueLength = postqueue.size();
 
    for(int j = 0; j < queueLength; j++)
    {
        cout << postqueue.front();
        if(isdigit(postqueue.front()))
        {
            var = postqueue.front();
            var1 = static_cast<float>(var);
            poststack.push(var1);
        }
 
        else if(postqueue.front() == '+' || '-' || '*' || '/' || '^')
        {
            temp2 = poststack.top();
            poststack.pop();
            temp1 = poststack.top();
            poststack.pop();
            switch(postqueue.front())
            {
                case '+': temp = temp1 + temp2;
                    break;
                case '-': temp = temp1 - temp2;
                    break;
                case '*': temp = temp1 * temp2;
                    break;
                case '/': temp = temp1 / temp2;
                    break;
                case '^': temp = pow(temp1, temp2);
                    break;
                default: cout << "There was a glitch in the operation, press any key to terminate.";
            }
 
            poststack.push(temp);
        }
        postqueue.pop();
    }
    final = poststack.top();
    cout << endl << "The postfix operation answer is: " << final << endl;
    return;
}