0 does not exit

[tm70]

I've been reading my code for the past 3 days and I cannot get 0 to exit the program. Any solution?

#include <iostream>
#include <cctype>
#include <cstring>
#include <cstdlib>
#include <fstream>

using namespace std;

size_t dub_count = 0;
size_t op_count = 0;

double answer = 0;
bool keep_going = true;
void reset();
void test_stacks();
void calculate();
struct dub_node
{
double data;
dub_node *next;
};

dub_node *dub_head = NULL;

void push_dub(double input)
{
dub_node *temp, *temp1;
temp1 = dub_head;
temp = new dub_node;
temp->data = input;
temp->next = dub_head;
dub_head = temp;
dub_count++;
}

double dub_peek()
{
if (dub_head != NULL)
return dub_head->data;
else return 9999999999.98739;
}

double dub_pop()
{
dub_node *temp;
if (dub_head == NULL)
{
return 9999999999.98739;
}
else
{
temp = dub_head;
dub_head = temp->next;
double ret_value = temp->data;
delete temp;
--dub_count;
return ret_value;
}
}

struct op_node
{
char data;
op_node *next;

};

op_node *op_head;

void push_op(char input)
{
op_node *temp, *temp1;
temp1 = op_head;
temp = new op_node;
temp->data = input;
temp->next = op_head;
op_head = temp;
op_count++;
}

char op_pop()
{
op_node *temp;
if (op_head == NULL)
{
return 'f';
}
else
{
temp = op_head;
op_head = temp->next;
char ret_value = temp->data;
delete temp;
--op_count;
return ret_value;
}
}

char op_peek()
{
if (op_head != NULL)
return op_head->data;
else return 'f';
}

void test_stacks()
{
if (op_count + 1 > dub_count)
{
cout << "Error: To many operators. Please try again.\n";
reset();
}
else if (op_count + 1 < dub_count)
{
cout << "Error: To many operands. Please try again.\n";
reset();
}
else
{
calculate();
}
}

void read_and_push(istream &ins)
{
const char DECIMAL = '.';
double number;
char op;

if (ins.peek() == 0){ keep_going = false; }
else
{
while (ins.peek() != '\n')
{
if (isdigit(ins.peek()) || ins.peek() == DECIMAL)
{
ins >> number;
push_dub(number);
}
else if (ins.peek() == '+' || ins.peek() == '-' || ins.peek() == '*' || ins.peek() == '/')
{
ins >> op;
push_op(op);
}
else
ins.ignore();
}
ins.ignore();
}
}

void reset()
{
char op_cursor;
op_cursor = op_peek();
while (op_cursor != 'f')
{
op_cursor = op_pop();
}
double dub_cursor;
dub_cursor = dub_peek();
while (dub_cursor != 9999999999.98739)
{
dub_cursor = dub_pop();
}
dub_head = NULL;
op_head = NULL;
dub_count = 0;
op_count = 0;
}

void calculate()
{
double operator1, operator2;
char operand;
do
{
answer = 0;
operator2 = dub_pop();
operator1 = dub_pop();
operand = op_pop();
switch (operand)
{
case '+':
answer = operator2 + operator1;
push_dub(answer);
break;
case '-':
answer = operator2 - operator1;
push_dub(answer);
break;
case '*':
answer = operator2 * operator1;
push_dub(answer);
break;
case '/':
if (operator1 == 0)
{
cout << "Error: Division by 0. Please try again.\n";
reset();
}
else
answer = operator2 / operator1;
push_dub(answer);
break;
}
} while (op_peek() != 'f');
}

int main()
{
cout << "Please input equations\n";
while (keep_going)
{
cout << "Type 0 to exit\n";
read_and_push(cin);
test_stacks();
cout << "\nAnswer is: " << dub_pop() << "\n";
reset();
};
return 0;
}

[LB]

Why is your program structured this way? You should validate input in main before proceeding to call any other function.

Global variables are bad.

[tm70]

I'm still new to programming. Do you know how I could make it so 0 will exit?

[LB]

while(true)
{
    int n;
    std::cin >> n;
    if(n == 0)
    {
        break;
    }
    //...
}

ne555's suggestion below ie better.

[ne555]

int n;
while( std::cin>>n and n not_eq 0 )
  //...