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# QStack Class Reference

The QStack class is a template class that provides a stack. More...

    #include <QStack>

Inherits QVector<T>.

Note: All the functions in this class are reentrant.

- List of all members, including inherited members

### Public Functions

- QStack ()
- ~QStack ()
- T pop ()
- void push ( const T & t )
- T & top ()
- const T & top () const

- 59 public functions inherited from QVector

## Detailed Description

The QStack class is a template class that provides a stack.

QStack<T> is one of Qt's generic container classes. It implements a stack data structure for items of a same type.

A stack is a last in, first out (LIFO) structure. Items are added to the top of the stack using push() and retrieved from the top using pop(). The top() function provides access to the topmost item without removing it.

Example:

        QStack<int> stack;
        stack.push(1);
        stack.push(2);
        stack.push(3);
        while (!stack.isEmpty())
            cout << stack.pop() << endl;

The example will output 3, 2, 1 in that order.

QStack inherits from QVector. All of QVector's functionality also applies to QStack. For example, you can use isEmpty() to test whether the stack is empty, and you can traverse a QStack using QVector's iterator classes (for example, QVectorIterator). But in addition, QStack provides three convenience functions that make it easy to implement LIFO semantics: push(), pop(), and top().

QStack's value type must be an assignable data type. This covers most data types that are commonly used, but the compiler won't let you, for example, store a QWidget as a value; instead, store a QWidget *.

See also QVector and QQueue.

## Member Function Documentation

### QStack::QStack ()

Constructs an empty stack.

### QStack::~QStack ()

Destroys the stack. References to the values in the stack, and all iterators over this stack, become invalid.

### T QStack::pop ()

Removes the top item from the stack and returns it. This function assumes that the stack isn't empty.

See also top(), push(), and isEmpty().

### void QStack::push ( const T & t )

Adds element t to the top of the stack.

This is the same as QVector::append().

See also pop() and top().

### T & QStack::top ()

Returns a reference to the stack's top item. This function assumes that the stack isn't empty.

This is the same as QVector::last().

See also pop(), push(), and isEmpty().

### const T & QStack::top () const

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

See also pop() and push().