The sample code below illustrates how to use the adjacent_difference and vector::push_back STL functions in Visual C++.
Required Header:
<numeric>
template<class InputIterator, class OutputIterator> inline
OutputIterator adjacent_difference(InputIterator first, InputIterator last, OutputIterator result)
template<class InputIterator, class OutputIterator, class BinaryOperator> inline
OutputIterator adjacent_difference(InputIterator first, InputIterator last, OutputIterator result,
BinaryOperator binary_op)
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:
Assigns to every element referred to by iterator i in the range [result + 1, result + (last - first)) a value correspondingly equal to *(first + (i - result)) - *(first + (i - result) - 1) or binary_op (*(first + (i - result)), *(first + (i - result) - 1)). Result gets the value of *first.
Sample Code:
///////////////////////////////////////////////////////////////////////
//
// Compile options needed: /GX
//
// adj_diff.cpp : Demonstrates the use of adjacent_difference()
//
// Description of adjacent_difference(first,last,result)
// adjacent_difference(first,last,result,binary_op):
//
// Assigns to every element referred to by iterator i in the range
// [result + 1, result + (last - first))
// a value correspondingly equal to
// *(first + (i - result)) - *(first + (i - result) - 1)
// or
// binary_op(*(first + (i - result)), *(first + (i - result) - 1)).
// Result gets the value of *first.
///////////////////////////////////////////////////////////////////////
#include <iostream>
#include <numeric>
#include <functional>
#include <vector>
#include <iterator>
using namespace std;
typedef vector < int > IntegerArray;
typedef ostream_iterator < int, char, char_traits<char> > IntOstreamIt;
void main ()
{
// an ostream iterator that outputs an int to cout terminated
// by a space
IntOstreamIt itOstream(cout," ");
// Initialize the array
// Suppose that you are taking a trip and can measure
// the miles traveled from your city of origin
// to the city you are traveling through
IntegerArray rgIA;
rgIA.push_back(5661); // San Francisco to Berlin
rgIA.push_back(7456); // to Cairo
rgIA.push_back(10995); // to Calcutta
rgIA.push_back(17019); // to Cape Town
rgIA.push_back(24394); // to Hong Kong
rgIA.push_back(30376); // to London
rgIA.push_back(35758); // to Los Angeles
// Print the array
copy(rgIA.begin(),rgIA.end(),itOstream);
cout << endl;
// Suppose that you now want the distance between each
// of the cities that you traveled to. You can easily
// find it with adjacent_difference()
IntegerArray rgDifferences(7);
IntegerArray::iterator itDifferences = rgDifferences.begin();
adjacent_difference(rgIA.begin(),rgIA.end(),itDifferences);
// Print the differences
// Remember that the first item in the differences array is
// not a difference, but is unused space
cout << "The adjacent differences are: ";
copy(rgDifferences.begin()+1,rgDifferences.end(),itOstream);
cout << endl;
// Suppose that you now want to know which adjacent differences
// are greater. If you have [a,b,c], you would like [1,0] if a>b
// and b<=c.
// You are using less() rather than greater() because
// adjacent_difference() reverses the parameters. For example,
// if a and b are adjacent, adjacent_difference() calls
// less(b,a). See the explanation at the top of this file
// for a more exact description.
IntegerArray rgGT(6);
IntegerArray::iterator itGT = rgGT.begin();
adjacent_difference(rgDifferences.begin()+1,
rgDifferences.end(),
itGT,
less<int>());
// Print the greater thans
// Remember that the first item in the differences array is
// not a difference, but is unused space
cout << "Which adjacent distances are greater:" << endl
<< "(If you have [a,b,c], then you have [1,0] if a>b and b<=c)"
<< endl;
copy(rgGT.begin()+1,rgGT.end(),itOstream);
cout << endl;
}
Program Output is:
5661 7456 10995 17019 24394 30376 35758
The adjacent differences are: 1795 3539 6024 7375 5982 5382
Which adjacent distances are greater:
(If you have [a,b,c], then you have [1,0] if a>b and b<=c)
0 0 0 1 1