INFO: (capacity size push_back) Functions

• The Standard C++ Library, used with:
  • Microsoft Visual C++, 32-bit Editions, versions 4.2, 5.0, 6.0

SUMMARY

The sample code below illustrates how to use the vector::size, vector::capacity, and vector::push_back functions.

MORE INFORMATION

Required Header

   <vector> 

Prototypes

   size_type vector::capacity() const
   size_type vector::size() const
   void vector::push_back(const _TYPE& _X) 

Description

• The sample declares an empty vector of integers.



• It outputs the size and capacity of the vector.



• It adds a single element to the vector, then outputs the size and capacity again.

Sample Code

////////////////////////////////////////////////////////////////////// 
// 
// Compile options needed: /GX
// 
// Capacity.cpp  - Illustrates vector::capacity and vector::size
// 
// Functions:
// 
//    vector::capacity  - Return # of elements for which memory has
//                        been allocated.
// 
//    vector::size      - Return # of elements in the vector
// 
//    vector::push_back - Append (insert) an element to the end of a
//                        vector, allocating memory for it if necessary.
// 
// Written by Tom Campbell
// of Microsoft Corporation
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
////////////////////////////////////////////////////////////////////// 

// The debugger can't handle symbols more than 255 characters long.
// STL often creates symbols longer than that.
// This disables the warning issued when symbols are longer than 255 chars.
#pragma warning(disable:4786)

#include <iostream>
#include <vector>

#if _MSC_VER > 1020   // if VC++ version is > 4.2
   using namespace std;  // std c++ libs implemented in std
   #endif

typedef vector<int, allocator<int> > INTVECTOR;

void main()
{
    // Dynamically allocated vector begins with 0 elements.
    INTVECTOR theVector;

    // Show size (current # of elements) and capacity (# of elements
    // there's room for) of the empty vector.
    cout << endl << "Vector with no elements:" << endl;
    cout << "theVector's size is: " << theVector.size() << endl;
    cout << "theVector's capacity is: " << theVector.capacity() << endl;

    // Add one element to the end of the vector, an int with the value 42.
    // Allocate memory if necessary.
    theVector.push_back(42) ;

    // Show size & capacity after adding an element to the vector.
    cout << endl << "After adding 1 element:" << endl;
    cout << "theVector's size is: " << theVector.size() << endl;
    cout << "theVector's capacity is: " << theVector.capacity() << endl;
} 

REFERENCES

Visual C++ Books On Line: Visual C++ Books:C/C++: Standard C++ Library Reference.

Additional query words: STL STLSample vector capacity size push_back

Keywords : kbcode kbVC420 kbVC500 kbVC600 kbDSupport STLIss
Version : winnt:4.2,5.0,6.0
Platform : winnt
Issue type : kbinfo