Develop c++ program to convert infix to postfix and evaluate the postfix expression:

1. Must use stack class created in different file(.h file and .cpp file) and NOT #include

2.Priority =

*, /

+, -

(

3) psudocode to implement:

Initialize an empty stack (for operators)

While not_finished parsing the expression

{obtain the next input token in the expression;

switch (token)

{case : break; //space

case (: push; break;

case ): pop & display popped element until ( is encountered;

//do not display the (

break;

case +, -, *, /, %: //( and ) are not considered as operators

if empty_stack or priority(token) > priority(stack_top)

push;

else

pop & display popped element until empty_stack or until

priority(token)<=priority(stack_top)

push

break;

case operand: display;

break;

} }

pop & display the rest of the stack elements; //do not display the (

}

here is what i have so far but not working:

//charstack.h

#pragma once #define CAPACITY 128 typedef int StackElement; class Charstack { StackElement stackArray[CAPACITY]; int stack_size; public: Charstack(); bool empty(); void push(StackElement item); StackElement pop(); StackElement top(); void display(); };

//charstack.cpp

#include "stdafx.h" #include using namespace std; #include "Charstack.h" #define CAPACITY 128 typedef int StackElement;

Charstack::Charstack() { stack_size = 0; } bool Charstack::empty() { if (stack_size == 0) return true; else return false; } StackElement Charstack::top() { if (stack_size >= 0) return (stackArray[stack_size]); else { cout << "Stack is empty "; } }

void Charstack::push(StackElement item) { if (stack_size == CAPACITY) cout << "stack is full "; else { stackArray[stack_size] = item; stack_size++; } } StackElement Charstack::pop() { stack_size--; if (stack_size >= 0) return stackArray[stack_size]; else return '\0'; } void Charstack::display() { for (int i = stack_size - 1; i >= 0; i--) cout << stackArray[i] << " "; }

//main program

#include "stdafx.h" #include using namespace std; #include #include"Charstack.h"

//double compute(string postfix);//to convert string infixToPostFix(string exp); bool Operator(char x); int Priority(char oper); int rightParenthense(char oper); int higherPrecedence(char oper1, char oper2);

int main() { string expression = "1*3+4/3"; string postFix;

cout << "infix expression is: " << expression << " ";

postFix = infixToPostFix(expression);

cout << "Postfix expression is: " << postFix << " ";

//cout << "Compute answer for the postfix expression is " << compute(postFix(infixExp)) << " ";

return 0; }

string infixToPostFix(string expression) { string postfix_exp = ""; Charstack opStack;//char stack

for (int i = 0; i < expression.length(); i++) { if (expression[i] == ' ')continue;

else if (Operator(expression[i])) { while (!opStack.empty() && opStack.top() != '(' && higherPrecedence(opStack.top(), expression[i])) { postfix_exp += opStack.top(); opStack.pop(); } opStack.push(expression[i]); }

else if (Operator(expression[i])) { postfix_exp += expression[i]; }

else if (expression[i] == '(') { opStack.push(expression[i]); }

else if (expression[i] == ')') { while (!opStack.empty() && opStack.top() != '(') { postfix_exp += opStack.top(); opStack.pop(); } opStack.pop(); } } while (!opStack.empty()) { postfix_exp += opStack.top(); opStack.pop(); }

return postfix_exp; }

//double compute(string postfix) //{

//}

bool Operator(char x) { if (x == '+' || x == '-' || x == '*' || x == '/' || x == '$') return true;

return false;

}

int Priority(char oper) { int preced = -1; switch (oper) { case '+': case '-': return preced = 1; break; case '*': case '/': return preced = 2; break; case '(': return preced = 3; break; } }

int rightParenthense(char oper) { if (oper == '(') return true; return false;

}

int higherPrecedence(char oper1, char oper2) { int op1Priority = Priority(oper1); int op2Priority = Priority(oper2);

if (op1Priority == op2Priority) { if (rightParenthense(op1Priority))return false; else return true; }

else if (op1Priority > op2Priority) return true;

else return false;

}