1. ## Stack Postfix Calculator

I read a post about the same thing and didn't know how to comment on it so I just made a new thread. Here's the code and couldn't get it to run. If anyone could look at this and tell me what's wrong with it that'd be great. I get an answer, but its wrong, for example 23+ gives me 225.

Code:
```#include <iostream>
#include <iomanip>
using namespace std;

class node
{
public:
float number;
node *next;
};

node* push(node *stack, float data)
{
node *utility;
utility = new node;
utility -> number = data;
utility -> next = stack;
return utility;
}

node* pop(node *stack, float &data)
{
node *temp;
if (stack != NULL)
{
temp = stack;
data = stack -> number;
stack = stack -> next;
delete temp;
}
else cout << "\nERROR: Empty stack.\n";
return stack;
}

int main()
{
char ch = ' ';
node *utility, *top;

utility = new node;
utility -> number = 0;
utility -> next = NULL;
top = new node;
top -> number = 0;
top -> next = utility;

while(ch != 'q')
{
cout << "calc> ";
cin >> noskipws >> ch;
if(ch == 'q')
{
return 0;
}
while(ch != '\n')
{

float operand = 0;
if((ch >= '0')&&(ch <= '9'))
{
while(ch != '\n')
{
operand = operand*10 + (ch-48);

cin >> ch;
}
top = push(top, operand);
}
else
{
if((ch == '+')||(ch == '-')||(ch == '*')||(ch == '/')){
top = pop(top, operand1);
top = pop(top, operand2);
switch(ch){
case '+': answer = operand2 + operand1;
break;
case '-': answer = operand2 - operand1;
break;
case '*': answer = operand2 * operand1;
break;
case '/': answer = operand2 / operand1;
break;
}
else {
cout << "Error! Wrong Character Entered";
}
}

}
}
}```

2. I can't find the error at first glance, but let me just ask you, why are you implementing your own stack for this? This has been done a million times before, don't reinvent the wheel, use std::stack, then you can focus on getting the RPN and arithmetics correct.

Also, why on earth would you use a linked-list for a stack implementation? What's wrong with an array, seems much simpler! (Or even better, a std::vector!)

Though at some point, it's better to learn how to use a debugger.

Anyway.
Code:
```#include <iostream>
#include <iomanip>
using namespace std;

class node {
public:
float number;
node *next;
};

node *push(node * stack, float data)
{
node *utility;
utility = new node;
utility->number = data;
utility->next = stack;
return utility;
}

node *pop(node * stack, float &data)
{
node *temp;
if (stack != NULL) {
temp = stack;
data = stack->number;
stack = stack->next;
delete temp;
} else
cout << "\nERROR: Empty stack.\n";
return stack;
}

int main()
{
char ch = ' ';
node *utility, *top;

utility = new node;
utility->number = 0;
utility->next = NULL;
top = new node;
top->number = 0;
top->next = utility;

while (ch != 'q') {
cout << "calc> ";
cin >> noskipws >> ch;
if (ch == 'q') {
return 0;
}
while (ch != '\n') {
float operand = 0;
if ((ch >= '0') && (ch <= '9')) {
while (ch != '\n') {
operand = operand * 10 + (ch - 48);
cin >> ch;
}
cout << "Debug: pushed " << operand << endl;
top = push(top, operand);
} else {
if ((ch == '+') || (ch == '-') || (ch == '*') || (ch == '/')) {
top = pop(top, operand1);
top = pop(top, operand2);
cout << "Debug: popped " << operand1 << " " << operand2 << endl;
switch (ch) {
case '+':
break;
case '-':
break;
case '*':
break;
case '/':
break;
}