The sample code below illustrates how to use the
generate_n, begin, end, and size STL functions in Visual C++.
Back to the top
Required header
<algorithm>
Back to the top
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.
Back to the top
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.
Back to the top
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 }
Back to the top
For the same topic about generate_n, visit the following
MSDN Web site:
http://msdn.microsoft.com/library/en-us/vclang98/html/sample_generate_n_(STL_Sample).asp?frame=true (http://msdn.microsoft.com/library/en-us/vclang98/html/sample_generate_n_(STL_Sample).asp?frame=true)
Back to the top