Q158613: STL Sample for the vector::(front, back) Functions
Article: Q158613
Product(s): Microsoft C Compiler
Version(s): 4.2,5.0,6.0
Operating System(s):
Keyword(s): kbcode kbtemplate kbSTL kbVC420 kbVC500 kbVC600 kbDSupport
Last Modified: 27-MAR-2002
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The information in this article applies to:
- The Standard C++ Library, used with:
- Microsoft Visual C++, 32-bit Enterprise Edition, versions 4.2, 5.0, 6.0
- Microsoft Visual C++, 32-bit Professional Edition, versions 4.2, 5.0, 6.0
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0
- Microsoft Visual C++.NET (2002)
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SUMMARY
=======
The following sample code illustrates how to use the vector::front and
vector::back STL functions in Visual C++.
MORE INFORMATION
================
Required Header
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<vector>
Prototypes
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template<class _TYPE, class _A>
reference vector::front();
template<class _TYPE, class _A>
reference vector::back();
NOTE: The class/parameter names in the prototype may not match the version in the
header file. Some have been modified to improve readability.
Description
-----------
The sample declares an empty vector of integers with the members [100, 200, 300,
400]. It displays the first element of the vector using vector::front to obtain
it. It displays the last element of the vector using vector::back to obtain it.
It displays the number of elements of the vector using vector::size.
The sample erases the last element of the vector using vector::end()-1, and then
displays the new last element using vector::back. It erases the first element of
the vector using vector::begin, and then displays the new first element using
vector::front.
Finally, the sample displays the number of elements remaining in the vector using
vector::size.
Sample Code
-----------
NOTE: The first line in the sample code section says:
// Compile options needed: /GX
In VC++ .NET, /EHsc is set by default and is equivalent to /GX.
//////////////////////////////////////////////////////////////////////
//
// Compile options needed: /GX
//
// front.cpp: Illustrates the vector::front and vector::back methods.
//
// Functions:
//
// vector::front - Returns reference to first element of vector.
//
// vector::back - Returns reference to last element of vector.
//
// vector::push_back - Appends (inserts) an element to the end of a
// vector, allocating memory for it if necessary.
//
// vector::size - Returns number of elements in the vector.
//
// vector::begin - Returns an iterator to start traversal of the vector.
//
// vector::end - Returns an iterator for the last element of the vector.
//
// vector::erase - Deletes elements from a vector (single & range).
//
// 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.
// When symbols are longer than 255 characters, the warning is issued.
#pragma warning(disable:4786)
// disable warning C4267: possible loss of data,
// okay to ignore
#pragma warning(disable: 4267)
#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;
const ARRAY_SIZE = 4;
void main()
{
// Dynamically allocated vector begins with 0 elements.
INTVECTOR theVector;
// Intialize the array to contain the members [100, 200, 300, 400]
for (int cEachItem = 0; cEachItem < ARRAY_SIZE; cEachItem++)
theVector.push_back((cEachItem + 1) * 100);
cout << "First element: " << theVector.front() << endl;
cout << "Last element: " << theVector.back() << endl;
cout << "Elements in vector: " << theVector.size() << endl;
// Delete the last element of the vector. Remember that the vector
// is 0-based, so theVector.end() actually points 1 element beyond
// the end.
theVector.erase(theVector.end() - 1);
cout << endl << "After erasing last element, new last element is: "
<< theVector.back() << endl;
// Delete the first element of the vector.
theVector.erase(theVector.begin());
cout << "After erasing first element, new first element is: "
<< theVector.front() << endl;
cout << "Elements in vector: " << theVector.size() << endl;
}
Program Output
--------------
First element: 100
Last element: 400
Elements in vector: 4
After erasing last element, new last element is: 300
After erasing first element, new first element is: 200
Elements in vector: 2
REFERENCES
==========
Visual C++ Books Online: Visual C++ Books; C/C++; Standard C++ Library Reference
Additional query words: STL STLSample
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Keywords : kbcode kbtemplate kbSTL kbVC420 kbVC500 kbVC600 kbDSupport
Technology : kbVCsearch kbAudDeveloper kbVCLibrary
Version : :4.2,5.0,6.0
Issue type : kbinfo
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