The sample code below illustrates how to use the advance()
STL function in Visual C++.
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Because only random access iterators provide + and -
operators, the library provides two template functions, advance() and
distance().
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Required Header
<iterator>
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Prototype
template<class InIt, class Dist>
void advance(InIt& it, Dist n);
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Description
The advance function accepts two parameters:
| • | InIt: The iterator to advance. |
| • | Dist: The number of elements to increment the iterator by.
|
The advance function advances the iterator n times. If the
iterator is a random-access iterator type, the function evaluates the
expression as
iterator += n.
Otherwise, it performs each increment by evaluating:
++iterator.
If the iterator is an input or forward iterator type, n must not
be negative.
NOTE: The class/parameter names in the prototype may not match the
version in the header file. Some have been modified to improve readability.
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Sample Code
//////////////////////////////////////////////////////////////////////
//
// Compile options needed: /GX
//
// <filename> : Advance.cpp
//
// Functions:
//
// advance()
//
// Written by Linda Koontz
// of Microsoft Product Support Services,
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
//////////////////////////////////////////////////////////////////////
/* Compile options needed: /GX
*/
#include <iostream>
#include <string>
#include <list>
#if _MSC_VER > 1020 // if VC++ version is > 4.2
using namespace std; // std c++ libs implemented in std
#endif
#pragma warning (disable:4786)
typedef list<string, allocator<string> > STRLIST;
void main() {
STRLIST List;
STRLIST::iterator iList;
STRLIST::difference_type dTheDiff;
List.push_back("A1");
List.push_back("B2");
List.push_back("C3");
List.push_back("D4");
List.push_back("E5");
List.push_back("F6");
List.push_back("G7");
// Print out the list
iList=List.begin();
cout << "The list is: ";
for (int i = 0; i < 7 ; i++, iList++)
cout << *iList << " ";
// Initialize to the first element"
iList=List.begin();
cout << "\n\nAdvance to the 3rd element." << endl;
advance(iList,2);
cout << "The element is " << *iList << endl;
dTheDiff = distance( List.begin(), iList);
}
Program Output is:
The list is: A1 B2 C3 D4 E5 F6 G7
Advance to the 3rd element.
The element is C3
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Visual C++ Books On Line: Visual C++ Books:C/C++:Standard
C++ Library Reference.
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