Undeclared identifier error when item is declared

Question

This is my header file for my static stack class, which is straight copied from my text book like it was supposed to be

#ifndef STACK_H
#define STACK_H
#include <iostream>
using namespace std;

// Stack template
template <class T>
class Stack
{
private:
    T *stackArray;
    int stackSize;
    int top;

public:
    // Constructor
    Stack(int);

    // Copy constructor
    Stack(const Stack&);

    // Destructor
    ~Stack();

    // Stack operations
    void push(T);
    void pop(T &);
    bool isFull();
    bool isEmpty();
};

//***************************************************
// Constructor *
//***************************************************

template <class T>
Stack<T>::Stack(int size)
{
    stackArray = new T[size];
    stackSize = size;
    top = −1;
}

//***************************************************
// Copy constructor *
//***************************************************


template <class T>
Stack<T>::Stack(const Stack &obj)
{
    // Create the stack array.
    if (obj.stackSize > 0)
        stackArray = new T[obj.stackSize];
    else
        stackArray = nullptr;

    // Copy the stackSize attribute.
    stackSize = obj.stackSize;

    // Copy the stack contents.
    for (int count = 0; count < stackSize; count++)
        stackArray[count] = obj.stackArray[count];

    // Set the top of the stack.
    top = obj.top;
}

//***************************************************
// Destructor *
//***************************************************

template <class T>
Stack<T>::~Stack()
{
    if (stackSize > 0)
        delete[] stackArray;
}

//*************************************************************
// Member function push pushes the argument onto *
// the stack. *
//*************************************************************

template <class T>
void Stack<T>::push(T item)
{
    if (isFull())
    {
        cout << "The stack is full.\n";
    }
    else
    {
        top++;
        stackArray[top] = item;
    }
}

//*************************************************************
// Member function pop pops the value at the top *
// of the stack off, and copies it into the variable *
// passed as an argument. *
//*************************************************************


template <class T>
void Stack<T>::pop(T &item)
{
    if (isEmpty())
    {
        cout << "The stack is empty.\n";
    }
    else
    {
        item = stackArray[top];
        top--;
    }
}

//*************************************************************
// Member function isFull returns true if the stack *
// is full, or false otherwise. *
//*************************************************************

template <class T>
bool Stack<T>::isFull()
{
    bool status;

    if (top == stackSize − 1)
        status = true;
    else
        status = false;

    return status;
}

//*************************************************************
// Member function isEmpty returns true if the stack *
// is empty, or false otherwise. *
//*************************************************************

template <class T>
bool Stack<T>::isEmpty()
{
    bool status;

    if (top == −1)
        status = true;
    else
        status = false;

    return status;
}
#endif

this is my main.cpp

#include "Stack.h"
#include <stack>
#include <string>

int PostfixCalculator(string postfixExpression);
bool isOperator(const string& expression);
void performOp(const string& expression, stack<int>& calc);



int main(){

    string expression;
    cout << "Enter Postfix Expression" << endl;
    cin >> expression;

    PostfixCalculator(expression);

}

bool isOperator(const string& expression){

    string ops[] = { "-", "+", "*", "/" };
    for (int i = 0; i < 4; i++){
        if (expression == ops[i]){
            return true;
        }
    }
    return false;
}

void performOp(const string& expression, Stack<int>& calc){//const 
    int leftVal, rightVal, result;

    calc.pop(rightVal);
    calc.pop(leftVal);


    if (expression == "-"){
        result = leftVal - rightVal;
    }
    else if (expression == "+"){
        result = leftVal + rightVal;
    }
    else if (expression == "*"){
        result = leftVal * rightVal;
    }
    else{
        result = leftVal / rightVal;
    }
    cout << result << endl;
    calc.push(result);

};

int PostfixCalculator(string expression){


    int num;
    int size = expression.size();

    Stack<int> calc(size);
    Stack<int> copyCalc(calc);


    for (int i = 0; i < expression.size(); i++){
        char c = expression.at(i);
        if (c >= '0' && c <= '9'){
            c = num;
            copyCalc.push(num);
        }
        else if (isOperator(expression)){

        performOp(expression, copyCalc);
        }

    }

};

I keep getting this error: "Error 2 error C2065: '−1' : undeclared identifier

The error is happening here:

template <class T>
Stack<T>::Stack(int size)
{
    stackArray = new T[size];
    stackSize = size;
    top = −1;
}

it happens at "top = -1"

We're not psychics, tell us which line gives the error. Better yet, copy/paste the actual error from the compiler. — Mark Ransom
Your textbook puts using namespace std; in a header? That's a terrible practice. — Pete Becker
Namespaces exist for a reason. Blowing away std:: might be acceptable in a .cpp file, but imposing it on users through a header file is bad manners. — Pete Becker

Klitos Kyriacou Klitos Kyriacou · Accepted Answer · 2015-12-04T21:59:15

The −1 is not using the ASCII minus sign, but instead it's a typographical punctuation. Try using -1 instead.

Undeclared identifier error when item is declared

1 Answers