DOCUMENT:Q156347  26-MAR-2002  [visualc]
TITLE   :INFO: STL Sample for the generate_n Function
PRODUCT :Microsoft C Compiler
PROD/VER::4.2,5.0,6.0
OPER/SYS:
KEYWORDS:kbcode kbVC420 kbVC500 kbVC600 kbDSupport

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

MORE INFORMATION
================

Required Header
---------------

      <algorithm>

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

   #pragma warning(disable: 4786)

   #include <iostream>
   #include <vector>
   #include <algorithm>

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

   // 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<int> > 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:

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  }

REFERENCES
==========

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

Additional query words: STL STLSample generate_n begin end size

======================================================================
Keywords          : kbcode kbVC420 kbVC500 kbVC600 kbDSupport 
Technology        : kbVCsearch kbAudDeveloper kbVCNET kbVCLibrary
Version           : :4.2,5.0,6.0
Issue type        : kbinfo

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