Making a simple stack in C++ - c++

Question

Hi I am making a simple stack class in C++ and am new to C++. I am having a few errors that I cannot figure out what they mean. Some help would be greatly appreciated! Here is my code:
Stack.h
#ifndef SStack
#define SStack
#include <cstdlib>
#include <string>
class SStack
{
public:
// Constructor
SStack( int cap);
// Copy Constructor
SStack( const SStack& s );
~SStack( );
void push ( const std::string& s);
std::string& pop ();
std::string& top () const;
bool IsEmpty () const;
int size() const;
int getCapacity() const;
// NONMEMBER FUNCTIONS for the bag class
// Precondition: s1.size( ) + s2.size( ) <= s1.Capacity.
// Postcondition: The stack returned is the union of s1 and s2.
SStack operator +(const SStack& s2);
private:
int Capacity; // Capacity is the maximum number of items that a stack can hold
std::string *DynamicStack;
int used; // How many items are stored in the stack
};
#endif
Stack.cpp
#include "SStack.h"
#include <string>
#include <cstdlib>
#include <iostream>
using namespace std;
class SStack
{
public:
void SStack(int cap){
DyanmicStack = new string[cap];
Capacity = cap;
used = -1;
}
void SStack(const SStack& s){
DyanmicStack = new string[cap];
}
~SStack( ){
delete(DynamicStack);
}
void push(const string& s){
DynamicStack[used] = s;
used++;
}
string& pop(){
if(used==-1){
cout << "Error stack is empty";
return " ";
}
else{
used--;
return DynamicStack[used+1];
}
}
string& top () const{
if(used==-1){
cout << "Error stack is empty";
return " ";
}
else{
return DynamicStack[used];
}
}
bool isEmpty(){
return (used==-1);
}
int size(){
return (used+1);
}
int getCapacity(){
return Capacity;
}
private:
int Capacity; //How much the stack can hold
string* DynamicStack;
int used; //objects in the stack
};
And here are the errors:
SStack.h:11: error: expected unqualified-id before ‘int’
SStack.h:11: error: expected `)' before ‘int’
SStack.h:13: error: expected unqualified-id before ‘const’
SStack.h:13: error: expected `)' before ‘const’
SStack.h:14: error: expected class-name before ‘(’ token
SStack.h:25: error: ISO C++ forbids declaration of ‘operator+’ with no type
SStack.h:25: error: ISO C++ forbids declaration of ‘s2’ with no type
SStack.h:8: error: an anonymous union cannot have function members
SStack.h:31: error: abstract declarator ‘<anonymous class>’ used as declaration
SStack.cpp:11: error: expected unqualified-id before ‘int’
SStack.cpp:11: error: expected `)' before ‘int’
SStack.cpp:17: error: expected unqualified-id before ‘const’
SStack.cpp:17: error: expected `)' before ‘const’
SStack.cpp:21: error: expected class-name before ‘(’ token
SStack.cpp: In member function ‘std::string&<anonymous class>::pop()’:
SStack.cpp:33: error: invalid initialization of non-const reference of type ‘std::string&’ from a temporary of type ‘const char*’
SStack.cpp: In member function ‘std::string&<anonymous class>::top() const’:
SStack.cpp:44: error: invalid initialization of non-const reference of type ‘std::string&’ from a temporary of type ‘const char*’
SStack.cpp: At global scope:
SStack.cpp:8: error: an anonymous union cannot have function members
SStack.cpp:70: error: abstract declarator ‘<anonymous class>’ used as declaration

Answer 1

Your include guard has the same name as your class. Remember that the preprocessor is a very simplistic search/replace feature.
#define SStack
class SStack
{
public:
// Constructor
SStack( int cap);
becomes:
#define SStack
class
{
public:
// Constructor
( int cap);
One pattern is to name it the same as your header's filename, such as STACK_H.

Answer 2

First of all, as was already noted, the header guard is broken.
Now, onto the actual problems:
You have misunderstood how class definition works. Your header is largely correct, what is wrong is your .cpp file. You are redefining class that you already have defined inside the header file. The proper way to provide implementation of member function is this
void SStack::SStack(const SStack& s){
DyanmicStack = new string[cap];
} or in for clearer example:
void SStack::push(const string& s){
DynamicStack[used] = s;
used++;
}.
Basically, you have to prepend the classes's name before the function name.
Also, just by copy pasting this I've noticed typo in your code (see if you can spot it ;-) ), and I would recommend rethinking the design, even if it is just an exercise.

Answer 3

I realized the class Pila(stack) some times ago, this is my solution:
(sorry but I'm new.. so I don't know how to indent the code here)
file: pila.h
//nodo is the type of elements that class pila contains.
struct nodo
{
int dato;
nodo* precedente;
};
class pila
{
private:
nodo* ultimo;
public:
pila();
void push(int numero);
int pop();
};
file: pila.cpp
#include <iostream>
#include"pila.h"
using namespace std;
pila::pila()
{
ultimo=NULL; // punta all'ultimo nodo inserito
}
void pila::push(int numero)
{
nodo* nuovo;
nuovo=new struct nodo;
nuovo->dato=numero;
if(ultimo==NULL)
{
nuovo->precedente=NULL;
ultimo=nuovo;
}
else
{
nuovo->precedente=ultimo;
ultimo=nuovo;
}
}
int pila::pop()
{
if (ultimo==NULL)
{
return 0;
}
else
{
int prelevato=ultimo->dato;
ultimo=ultimo->precedente;
return prelevato;
}
}