I have to write a program which balances a string with brackets.I wrote the program but it doesn't matter which string I enter because the program always says that the string is good.
Here's the code:
header file
#ifndef HEADER_H_
#define HEADER_H_
#include <string>
struct Element {
char data;
Element* link;
};
typedef Element* Stack;
void initStack(Stack& S);
void push(Stack& S, int a);
void pop(Stack &S);
int top(Stack& S);
bool isEmpty(Stack &S);
bool goodPair(char deschis, char inchis);
bool check(std::string s);
#endif
functions file
#include <iostream>
#include <string>
#include "header.h"
using namespace std;
void initStack(Stack& S)
{
S = nullptr;
}
void push(Stack& S, int a)
{
Element*nou = new Element;
nou->data = a;
nou->link = S;
S = nou;
}
void pop(Stack& S)
{
Stack aux = S;
S = S->link;
delete(aux);
}
int top(Stack& S)
{
if (isEmpty(S))
return int();
return S->data;
}
bool isEmpty(Stack &S)
{
if (S == 0)
return true;
else
return false;
}
bool goodPair(char deschis, char inchis)
{
if (deschis == '(' && inchis == ')')
return true;
else if (deschis == '[' && inchis == ']')
return true;
else if (deschis == '{' && inchis == '}')
return true;
else if (deschis == '<' && inchis == '>')
return true;
else
return false;
}
bool check(std::string s)
{
Element* S;
for (int i = 0; i < s.length(); i++)
{
if (s[i] == '(' || s[i] == '[' || s[i] == '{' || s[i] == '<')
push(S, s[i]);
else
{
if (s[i] == ')' || s[i] == ']' || s[i] == '}' || s[i] == '>')
if (isEmpty(S) || !goodPair(top(S), s[i]))
return false;
else
pop(S);
}
}
if (isEmpty(S))
return false;
else
return true;
}
main file
#include <iostream>
#include <string>
#include "header.h"
using namespace std;
int main()
{
Stack S;
initStack(S);
string s;
cout << "Write the string:";
cin >> s;
if (check(s))
cout << "Good";
else
cout << "Bad";
return 0;
}
I used a stack and I traversed each character.If the character is an opening bracket I put it in the stack.When the character is a closing bracket, I compare it with the top of the stack.If it's good I pop the top of the stack.
You create a pointer to Element (aliased as Stack) S in main() and initialize it with nullptr using initStack() and then you do not use this variable anymore. Instead you create a local S in function check() and use it uninialized, which leads to UB.
Looks like you get confused by naming as you call of them S (variable in main(), variable in check(), all reference parameters all called S). It is not illegal to do so, but looks like you confused yourself. (you even called std::string lowercase s to increase confusion)
Also you have logical error in your function:
if (isEmpty(S))
return false;
else
return true;
should be opposite, if stack is empty then string is balanced, not vice versa. So replace it with:
return isEmpty( S );
I need to check if number of letters "a" is equal to number of letters "b" using stack.
So i understand logic of this task, but my code doesn't work.
Logic:
If current letter == to letter in stack (s.pop()) or stack is empty then push into stack
else pop from stack
after end of cycle check size of stack. If it is empty so number of letters is equl, else not
I already have class stack
#include <string>
#include <iostream>
#include <cstdlib> // для system
using namespace std;
class stack {
public:
stack() {
ptr = 0;
}
~stack() {}
bool push(int val) {
if (ptr >= MAXSIZE) return false;
body[ptr++] = val; return true;
}
bool pop(int *val) {
if (ptr == 0) return false;
*val = body[--ptr]; return true;
}
bool empty() {
return ptr == 0;
}
private:
enum { MAXSIZE = 100 };
int body[MAXSIZE];
int ptr; // указатель на последний элемент
};
int main()
{
stack s;
std::string str;
std::cout << "Enter your ab string ";
getline(std::cin, str);
for (int c : str) {
if (c == s.pop(&c) || s.empty()) {
s.push(c);
}
else {
s.pop(&c);
}
}
if (s.empty()) {
cout << "YES\n";
system("pause");
return 0;
}
else {
cout << "NO\n";
system("pause");
}
}
result for abab, aabb, ab 'YES'
for aaabb, aba 'NO'
You need a method to look at current value on top of stack without popping it:
class stack {
...
int top() { // never use on an empty stack
return body[ptr-1];
}
...
};
That way you can write:
for (int c : str) {
// short circuit evaluation ensures that top is never called on an empty stack
if (s.empty() || (c == s.top()) {
s.push(c);
}
else {
s.pop(&c);
}
If you cannot, you must push back the popped value if it should not have been popped:
for (int c : str) {
int d;
if (! s.pop(&d)) { // s was empty
s.push(c);
}
else if (c == d) {
s.push(d); // should not have been popped
s.push(c);
}
}
You can push everytime you see a.
for (int c = 0; c < str.size() ; ++c) {
if (str[c] == 'a') s.push('a');
}
if ((s.size() * 2) == str.size()) cout << "YES\n"; else cout << "NO\n";
stack::size can be implemented this way:
int stack::size() {
return ptr;
}
I'm trying to write a simple program to convert infix notation to prefix and postfix. So far the postfix one works perfectly. However, I can't seem to get the prefix conversion right. I used the shunting yard algorithm for both. Apologies beforehand if my code is a bit unusual (i.e. writing my own stack class instead of using #include, unnecessarily using other things), I have to meet assignment requirements (this is a college assignment). Here's what I've tried so far:
#include<iostream>
#include<string.h>
using namespace std;
const int Max=255;
class Stack
{
private:
char element[Max];
int top;
public:
Stack()
{
top=-1;
}
bool isFull()
{
if(top>=(Max-1)) return true;
else return false;
}
bool isEmpty()
{
if(top==-1) return true;
else return false;
}
bool push(char x)
{
if(!isFull())
{
top++;
element[top]=x;
return true;
}
else
{
cout<<"Stack is full"<<endl;
return false;
}
}
bool pop(char &x)
{
if(!isEmpty())
{
x=element[top--];
return true;
}
else
{
//cout<<"Stack is empty"<<endl;
return false;
}
}
char retrieve()
{
if(!isEmpty())
{
return element[top];
}
else
{
//cout<<"Stack is empty"<<endl;
return ' ';
}
}
};
class Converter
{
private:
public:
Converter(){}
bool isOperator(char x)
{
if(x=='+'||x=='-'||x=='*'||x=='/'||x=='^'||x=='('||x==')') return true;
else return false;
}
bool isOperand(char x)
{
if(x>='0'&&x<='9') return true;
else return false;
}
int Hierarchy(char x)
{
if(x=='+'||x=='-') return 1;
else if(x=='*'||x=='/') return 2;
else if(x=='^') return 3;
else return 0;
}
char*ToPostfix(char infix[])
{
Stack stack1;
char res[20];
int resindex=0;
for(int i=0;i<strlen(infix);i++)
{
if(isOperator(infix[i]))
{
if(infix[i]=='(')
{
stack1.push(infix[i]);
}
else if(infix[i]==')')
{
while(stack1.retrieve()!='(')
{
stack1.pop(res[resindex++]);
}
stack1.pop(res[resindex]);
}
else
{
while(Hierarchy(infix[i])<=Hierarchy(stack1.retrieve()))
{
stack1.pop(res[resindex++]);
}
stack1.push(infix[i]);
}
}
else if(isOperand(infix[i]))
{
res[resindex++]=infix[i];
}
}
while(!stack1.isEmpty())
{
stack1.pop(res[resindex++]);
}
res[resindex]='\0';
return res;
}
char*ToPrefix(char infix[])
{
char res[20];
strcpy(res,strrev(infix));
for(int i=0;i<strlen(res);i++)
{
if(res[i]=='(')
{
res[i]=')';
}
else if(res[i]==')')
{
res[i]='(';
}
}
strcpy(res,ToPostfix(res));
strcpy(res,strrev(res));
return res;
}
};
int main()
{
Converter convert;
char infix[20];
cout<<"Enter infix expression: ";
cin>>infix;
cout<<endl<<"Prefix: "<<convert.ToPrefix(infix)<<endl;
cout<<"Postfix: "<<convert.ToPostfix(infix)<<endl;
return 0;
}
when I try to convert a simple infix notation, i.e. 1*(2+3)/4^5-6, the postfix conversion is right (123+*45^/6-) but the prefix conversion returns the wrong answer (-*1/+23^456) instead of -/*1+23^456. can anyone help?
Actually, both answers are correct because you can switch the order of the division and the multiplication if multiplication comes first in infix. So your wrong answer is correct in this case. However, there is a left to right precedence, so your hierarchy handling is not correct: change else if(x=='*'||x=='/') return 2;.
I wrote this program and it supposed to test for the correct use of the three grouping symbols "(",")";"[","]"; and "{","}". It is using the array implementation of the stacks and supposed to evaluate if it is good string or a bad string. For example: (a+b), [(a-b)+c] would be good and )a+b( etc. would be bad string. When i run the program i get only one error. I thought i am missing a semi-colon or something, but after looking through the code several time,i can't find it. Maybe i got tunnel vision. Can you please see what the problem here is? This is the error: project1.cpp:41: error: expected initializer before 'while'.
#include <string>
#include <iostream>
#include <stdio.h>
using namespace std;
const int DefaultListSize = 100;
typedef char Elem;
class Astack {
private:
int size;
int top;
Elem *listArray;
public:
Astack (int sz = DefaultListSize)
{size = sz; top= 0; listArray = new Elem[sz];}
~Astack() {delete [] listArray;}
void clear() {top=0;}
bool push(const Elem& item) {
if (top == size) return false;
else {listArray[top++] = item; return true;}}
bool pop(Elem& it) {
if (top==0) return false;
else {it = listArray[--top]; return true;}}
bool topValue(Elem& it) const {
if (top==0) return false;
else {it = listArray[top-1]; return true;}}
bool isEmpty() const {if (top==0) return true;
else return false;}
int length() const{return top;}
}; //end of class Astack
Astack s;
const string LEFTGROUP="([{";
const string RIGHTGROUP=")]}";
int main()
while (!EOF) {
while (!EOL) {
ch = getc();
if (ch == LEFTGROUP[0]) {
s.push(ch);
}
if (ch == LEFTGROUP[1] {
s.push(ch);
}
if (ch == LEFTGROUP[2] {
s.push(ch);
}
} //checking for openers
while (!EOL) {
ch = getc();
if (s.top() == LEFTGROUP[0]) {
if (ch == RIGHTGROUP[0]) {
s.pop();
}
}
if (s.top() == LEFTGROUP[1]) {
if (ch == RIGHTGROUP[1]) {
s.pop();
}
}
if (s.top() == LEFTGROUP[2]) {
if (ch == RIGHTGROUP[2]) {
s.pop();
}
}
if (!s.empty()) {
cout<<"Bad String."<<endl;
else {
cout<<"Good String."endl;
}
}
}
return 0;
You forgot a { at the beginning of int main(). You should also end with }
int main(){
//your while code
return 0;
}
Problem Statement :
Write a C++ program to evaluate postfix expressions. Your program should take postfix expression as an input, process it with the help of stack and display the result after performing required calculations.
Only following Binary operators are allowed for this program:
+, -, *, /, ^ [addition, subtraction, multiplication, division, exponentiation]
If some error occurs while processing postfix expression, your program should display a meaningful message, like:
Error: Division by zero not allowed
Error: Two operands required for __ operator
Error: Invalid postfix expression
Help me with it, My program is generating errors This is my try:
#include<iostream>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<string>
#define MAX_SIZE 20
using namespace std;
template<class T>
class Stack
{
private:
T item[MAX_SIZE];
int top;
public:
Stack()
{
top = -1;
}
void push(T data)
{
if(!this->is_full())
item[++top] = data;
else
{
cout<<"Stack Error"<<endl;
exit(10);
}
}
T pop()
{
if(!this->is_empty())
return item[top--];
else
{
cout<<"Stack is Empty"<<endl;
exit(11);
}
}
int size()
{
return top+1;
}
bool is_empty()
{
if(top==-1)
return true;
else
return false;
}
bool is_full()
{
if(top==MAX_SIZE-1)
return true;
else
return false;
}
void display()
{
for(int i=0; i<this->size(); i++)
{
cout<<item[i]<<" ";
}
cout<<endl;
}
T return_top()
{
return item[top];
}
};
class Convert
{
private:
bool num_flag;
bool tow_digit_flag;
public:
Convert();
string return_with_bracket(string infix);
void to_Postfix(string infix,char postfix[]);
bool prcd(char op1, char op2);
int isOperand(char op);
int isOperator(char op);
bool return_flag()
{
return num_flag;
}
};
Convert::Convert()
{
this->num_flag = false;
this->tow_digit_flag = false;
}
string Convert::return_with_bracket(string infix)
{
return("(" + infix + ")");
}
bool Convert::prcd(char op1, char op2)
{
if((op1=='+' || op1=='-' || op1=='*' || op1=='/') && op2=='(' )
return true;
if(op1=='+' && op2=='+')
return true;
if(op1=='-' && op2=='-')
return false;
if(op1=='-' && op2=='+')
return false;
if(op1=='+' && op2=='-')
return false;
if(op1=='/' && op2=='/')
return false;
if(op1=='/' && (op2=='-' || op2=='+'))
return true;
if(op1=='*' && (op2=='+' || op2=='-'))
return true;
if((op1 == '-' || op1 == '+') && (op2 =='*' || op2 == '/'))
return false;
if((op1=='$' || op1 == '+') && (op2 =='*' || op2 == '/' || op2=='-'))
return true;
if((op1 == '-' || op1 == '+' || op1 =='*' || op1 == '/')&& op2=='^')
return false;
if(op1 == '^' && ( op2 == '+' || op2 =='*' || op2 == '/' || op2=='-'))
return false;
}
int Convert::isOperand(char op)
{
return(op>= '0' && op <= '9');
}
int Convert::isOperator(char op)
{
return(op=='+' || op=='-' || op == '/' || op=='*' || op=='^');
}
void Convert::to_Postfix(string infix, char postfix[])
{
int position, outpos=0;
char c;
int count = 0;
char temp;
char stacktop ;
Stack<char> stack;
for(position = 0; (c = infix[position])!='\0'; position++)
{
if(this->isOperand)
{
postfix[outpos++] = c;
this->num_flag = true;
count++;
if(count>=2)
{
this->tow_digit_flag = true;
}
}
else if(this->isOperator©)
{
count = 0;
if(isOperator(infix[position]) && isOperator(infix[position+1]))
{
cout<<"\aMissing argument in between "<<infix[position]<<" and "<<infix[position+1]
<<" in column "<< position+1<<endl;
exit(9);
}
if(this->prcd(c, stacktop))
{
stacktop=stack.return_top();
stack.push©;
stacktop = c;
}
else
{
while(true)
{
temp = stack.pop();
postfix[outpos++] =temp;
stacktop = stack.return_top();
if(prcd(c, stacktop) || stacktop=='(')
break;
}
stack.push©;
stacktop = stack.return_top();
}
}
else if(c=='(')
{
count = 0;
stack.push©;
stacktop = stack.return_top();
}
else if(c==')')
{
count = 0;
while(1)
{
if(stack.size()==0)
{
cout<<"Warning!! Number of ')' is greater than '('" <<endl;
exit(2);
}
temp = stack.pop();
if(temp!='(')
{
postfix[outpos++] = temp;
}
else
{
break;
}
}
stacktop =stack.return_top();
}
else
{
cout<<"Invalid input";
exit(3);
}
if(infix[position]==')' && infix[position+1]=='(')
{
stack.push('*');
stacktop = stack.return_top();
}
}
if(stack.size()!=0)
{
cout<<"Warning!!Number of '(' is greater than ')'"<<endl;
// exit(6);
}
if(!this->return_flag())
{
cout<<"You must Enter Numeric value for calculation"<<endl;
cout<<"This program cannot perform operations on variables";
exit(5);
}
if(this->tow_digit_flag)
{
cout<<"Sory! Althoug u may have entered right string"<<endl;
cout<<"this program is only for single digit operation"<<endl;
exit(8);
}
postfix[outpos] = '\0';
}
class Evaluate
{
public:
double eval(char expr[], Convert &Wink;
double oper(int symb, double op1, double op2);
};
double Evaluate::oper(int symb, double op1, double op2)
{
switch(symb)
{
case '+':
return (op1 + op2);
case '-':
return (op1 - op2);
case '*':
return (op1 * op2);
case '/':
return (op1 / op2);
case '^':
return (pow(op1, op2));
}
}
double Evaluate::eval(char expr[],Convert &convert)
{
int c, position;
char temp1;
int count = 0;
double opnd1, opnd2, value;
Stack<double> stack;
for(position = 0; (c = expr[position])!='\0'; position++)
{
if(convert.isOperand©)
{
temp1 = double(c-'0');
stack.push(temp1);
}
else
{
opnd2 = stack.pop();
if(stack.size()==0)
{
cout<<"This program cannot process unary operation";
exit(1);
}
opnd1 = stack.pop();
value = oper(c, opnd1, opnd2);
stack.push(value);
}
}
if(stack.size()>=2)
{
cout<<"Sory! this program cannot calculate this"<<endl;
cout<<"Enter +, *, /, - or ^ between bracket"<<endl;
exit(4);
}
return (stack.pop());
}
int main()
{
Convert convert;
Evaluate evaluate;
string bracketted_infix;
char infix[50], postfix[50];
char choice;
while(1)
{
cout<<"Enter operation: ";
cin>>infix;
cout<<endl;
cout<<"Entered operation: "<<infix<<endl;
bracketted_infix = convert.return_with_bracket(infix);
convert.to_Postfix(bracketted_infix, postfix);
cout<<"Equivalent Postfix operation: "<<postfix<<endl;
cout<<"RESULT: ";
cout<<evaluate.eval(postfix, convert);
cout<<"\nCalculate another operation?(y/n) ";
cin>>choice;
cout<<endl;
if(choice=='n')
break;
}
return 0;
}
To get it actually compiling you need to fix two syntax errors;
On line 154 you are calling a method with no parameter,
but the only declaration of this method takes 1 parameter.
if (this->isOperand) {
I believe you may have meant:
if (this->isOperand(c)) {
Also on line 255 you have a missing bracket before the semicolon:
double eval(char expr[], Convert &Wink;
When I actually ran your code it failed at runtime, with VS2010 giving an error "string subscript out of range".
If you're not already, I would recommend using a good IDE (such as Visual C++) when developing; the syntax colouring and support for dynamic debugging (i.e. breakpoints and watches) would be very helpful to debug a program like this.
Here is the final solution
#include<iostream>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<string>
#define MAX_SIZE 20
using namespace std;
template<class T>
class Stack
{
private:
T item[MAX_SIZE];
int top;
public:
Stack()
{
top = -1;
}
void push(T data)
{
if(!this->is_full())
item[++top] = data;
else
{
cout<<"Stack Error"<<endl;
exit(10);
}
}
T pop()
{
if(!this->is_empty())
return item[top--];
else
{
cout<<"Stack is Empty"<<endl;
exit(11);
}
}
int size()
{
return top+1;
}
bool is_empty()
{
if(top==-1)
return true;
else
return false;
}
bool is_full()
{
if(top==MAX_SIZE-1)
return true;
else
return false;
}
void display()
{
for(int i=0; i<this->size(); i++)
{
cout<<item[i]<<" ";
}
cout<<endl;
}
T return_top()
{
return item[top];
}
};
class Convert
{
private:
bool num_flag;
bool tow_digit_flag;
public:
Convert();
string return_with_bracket(string infix);
void to_Postfix(string infix,char postfix[]);
bool prcd(char op1, char op2);
int isOperand(char op);
int isOperator(char op);
bool return_flag()
{
return num_flag;
}
};
Convert::Convert()
{
this->num_flag = false;
this->tow_digit_flag = false;
}
string Convert::return_with_bracket(string infix)
{
return("(" + infix + ")");
}
bool Convert::prcd(char op1, char op2)
{
if((op1=='+' || op1=='-' || op1=='*' || op1=='/') && op2=='(' )
return true;
if(op1=='+' && op2=='+')
return true;
if(op1=='-' && op2=='-')
return false;
if(op1=='-' && op2=='+')
return false;
if(op1=='+' && op2=='-')
return false;
if(op1=='/' && op2=='/')
return false;
if(op1=='/' && (op2=='-' || op2=='+'))
return true;
if(op1=='*' && (op2=='+' || op2=='-'))
return true;
if((op1 == '-' || op1 == '+') && (op2 =='*' || op2 == '/'))
return false;
if((op1=='$' || op1 == '+') && (op2 =='*' || op2 == '/' || op2=='-'))
return true;
if((op1 == '-' || op1 == '+' || op1 =='*' || op1 == '/')&& op2=='^')
return false;
if(op1 == '^' && ( op2 == '+' || op2 =='*' || op2 == '/' || op2=='-'))
return false;
}
int Convert::isOperand(char op)
{
return(op>= '0' && op <= '9');
}
int Convert::isOperator(char op)
{
return(op=='+' || op=='-' || op == '/' || op=='*' || op=='^');
}
void Convert::to_Postfix(string infix, char postfix[])
{
int position, outpos=0;
char c;
int count = 0;
char temp;
char stacktop ;
Stack<char> stack;
for(position = 0; (c = infix[position])!='\0'; position++)
{
if (this->isOperand(c))
{
postfix[outpos++] = c;
this->num_flag = true;
count++;
if(count>=2)
{
this->tow_digit_flag = true;
}
}
else if(this->isOperator(c))
{
count = 0;
if(isOperator(infix[position]) && isOperator(infix[position+1]))
{
cout<<"\aMissing argument in between "<<infix[position]<<" and "<<infix[position+1]
<<" in column "<< position+1<<endl;
exit(9);
}
if(this->prcd(c, stacktop))
{
stacktop=stack.return_top();
stack.push(c);
stacktop = c;
}
else
{
while(true)
{
temp = stack.pop();
postfix[outpos++] =temp;
stacktop = stack.return_top();
if(prcd(c, stacktop) || stacktop=='(')
break;
}
stack.push(c);
stacktop = stack.return_top();
}
}
else if(c=='(')
{
count = 0;
stack.push(c);
stacktop = stack.return_top();
}
else if(c==')')
{
count = 0;
while(1)
{
if(stack.size()==0)
{
cout<<"Warning!! Number of ')' is greater than '('" <<endl;
exit(2);
}
temp = stack.pop();
if(temp!='(')
{
postfix[outpos++] = temp;
}
else
{
break;
}
}
stacktop =stack.return_top();
}
else
{
cout<<"Invalid input";
exit(3);
}
if(infix[position]==')' && infix[position+1]=='(')
{
stack.push('*');
stacktop = stack.return_top();
}
}
if(stack.size()!=0)
{
cout<<"Warning!!Number of '(' is greater than ')'"<<endl;
// exit(6);
}
if(!this->return_flag())
{
cout<<"You must Enter Numeric value for calculation"<<endl;
cout<<"This program cannot perform operations on variables";
exit(5);
}
if(this->tow_digit_flag)
{
cout<<"Sory! Althoug u may have entered right string"<<endl;
cout<<"this program is only for single digit operation"<<endl;
exit(8);
}
postfix[outpos] = '\0';
}
class Evaluate
{
public:
double eval(char expr[], Convert &Wink);
double oper(int symb, double op1, double op2);
};
double Evaluate::oper(int symb, double op1, double op2)
{
switch(symb)
{
case '+':
return (op1 + op2);
case '-':
return (op1 - op2);
case '*':
return (op1 * op2);
case '/':
return (op1 / op2);
case '^':
return (pow(op1, op2));
}
}
double Evaluate::eval(char expr[],Convert &convert)
{
int c, position;
char temp1;
int count = 0;
double opnd1, opnd2, value;
Stack<double> stack;
for(position = 0; (c = expr[position])!='\0'; position++)
{
if(convert.isOperand(c))
{
temp1 = char(c-'0');
stack.push(temp1);
}
else
{
opnd2 = stack.pop();
if(stack.size()==0)
{
cout<<"This program cannot process unary operation";
exit(1);
}
opnd1 = stack.pop();
value = oper(c, opnd1, opnd2);
stack.push(value);
}
}
if(stack.size()>=2)
{
cout<<"Sory! this program cannot calculate this"<<endl;
cout<<"Enter +, *, /, - or ^ between bracket"<<endl;
exit(4);
}
return (stack.pop());
}
int main()
{
Convert convert;
Evaluate evaluate;
string bracketted_infix;
char infix[50], postfix[50];
char choice;
while(1)
{
cout<<"Enter operation: ";
cin>>infix;
cout<<endl;
cout<<"Entered operation: "<<infix<<endl;
bracketted_infix = convert.return_with_bracket(infix);
convert.to_Postfix(bracketted_infix, postfix);
cout<<"Equivalent Postfix operation: "<<postfix<<endl;
cout<<"RESULT: ";
cout<<evaluate.eval(postfix, convert);
cout<<"\nCalculate another operation?(y/n) ";
cin>>choice;
cout<<endl;
if(choice=='n')
break;
}
return 0;
}