Microsoft KB Archive/156347

= How to use the generate_n, begin, end, and size Standard Template Library (STL) functions in Visual C++ =

Article ID: 156347

Article Last Modified on 7/15/2005

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APPLIES TO

 The Standard C++ Library, when used with:  Microsoft Visual C++ 4.2 Enterprise Edition

 Microsoft Visual C++ 5.0 Enterprise Edition

 Microsoft Visual C++ 6.0 Enterprise Edition

 Microsoft Visual C++ 4.2 Professional Edition</li></ul>

 Microsoft Visual C++ 5.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Standard Edition</li></ul>

 Microsoft Visual C++ .NET 2003 Standard Edition</li></ul>

 Microsoft Visual C++ .NET 2002 Standard Edition</li></ul> </li></ul>

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This article was previously published under Q156347

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SUMMARY
The sample code below illustrates how to use the generate_n, begin, end, and size STL functions in Visual C++.

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Prototype
template<class OutputIterator, class Size, class Generator> inline

void generate_n(OutputIterator first, Size n, Generator gen) Note The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

Description
The generate_n algorithm traverses the range [first, first + n) assigning to each element the value returned by gen. Note that generate modifies the elements in the specified range.

Sample code
Note In the first line of the sample code section, /GX is equivalent to /EHsc in VC++ .NET and is set by default. ////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX // // generate_n.cpp : Illustrates how to use the generate_n function. // // Functions: // //  generate_n  - Fill a specified number of elements of a sequence //                using a generator function. // //  begin       - Returns an iterator that points to the first element //                in a sequence. // //  end         - Returns an iterator that points one past the end of //                 a sequence. // //  size        - Returns the length of a sequence. // // Written by Kalindi Sanghrajka // of Microsoft Product Support Services, // Software Core Developer Support. // Copyright (c) 1996 Microsoft Corporation. All rights reserved. //////////////////////////////////////////////////////////////////////

// disable warning C4786: symbol greater than 255 character, // okay to ignore


 * 1) pragma warning(disable: 4786)


 * 1) include
 * 2) include
 * 3) include

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

// return the next Fibonacci number in the // Fibonacci series. int Fibonacci(void)

{

static int r;   static int f1 = 0; static int f2 = 1; r = f1 + f2 ; f1 = f2 ; f2 = r ; return f1 ;

}

void main

{

const int VECTOR_SIZE = 15 ;

// Define a template class vector of integers typedef vector<int, allocator > IntVector ;

//Define an iterator for template class vector of integer typedef IntVector::iterator IntVectorIt ;

IntVector Numbers(VECTOR_SIZE) ;  //vector containing numbers

IntVectorIt start, end, it ;

int i ;

//Initialize vector Numbers for(i = 0; i < VECTOR_SIZE; i++) Numbers[i] = i * i ;

start = Numbers.begin ;  // location of first // element of Numbers

end = Numbers.end ;      // one past the location // last element of Numbers

cout << "Before calling generate_n" << endl ;

// print content of Numbers cout << "Numbers { " ; for(it = start; it != end; it++) cout << *it << " " ; cout << " }\n" << endl ;

// fill the specified range with a series of   // Fibonacci numbers using the Fibonacci function generate_n(start + 5, Numbers.size - 5, Fibonacci) ;

cout << "After calling generate_n" << endl ;

// print content of Numbers cout << "Numbers { " ; for(it = start; it != end; it++) cout << *it << " " ; cout << " }\n" << endl ;

} Program Output is: <pre class="fixed_text">Before calling generate_n Numbers { 0 1 4 9 16 25 36 49 64 81 100 121 144 169 196 }

After calling generate_n Numbers { 0 1 4 9 16 1 1 2 3 5 8 13 21 34 55 }

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