Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc.

NAME

  adjacent_difference  - Outputs a sequence of the differences between each
  adjacent pair of elements in a range.

SYNOPSIS

  #include <numeric>

  template <class InputIterator, class OutputIterator>
  OutputIterator adjacent_difference (InputIterator first,
                                     InputIterator last,
                                     OutputIterator result);
  template <class InputIterator,
           class OutputIterator,
           class BinaryOperation>
  OutputIterator adjacent_difference (InputIterator first,
                                     InputIterator last,
                                     OutputIterator result,
                                     BinaryOperation bin_op);

DESCRIPTION

  Informally, adjacent_difference fills a sequence with the differences
  between successive elements in a container.  The result is a sequence in
  which the first element is equal to the first element of the sequence being
  processed, and the remaining elements are equal to the calculated
  differences between adjacent elements.  For instance, applying
  adjacent_difference to {1,2,3,5} will produce a result of {1,1,1,2}.

  By default, subtraction is used to compute the difference, but you can
  supply any binary operator. The binary operator is then applied to adjacent
  elements.  For example, by supplying the plus (+) operator, the result of
  applying adjacent_difference to {1,2,3,5} is the sequence {1,3,5,8}.

  Formally, adjacent_difference assigns to every element referred to by
  iterator i in the range [result + 1, result + (last - first)) a value equal
  to the appropriate one of the following:

  *(first  + (i - result)) - *(first + (i - result) - 1)

   or

  binary_op (*(first + (i - result)), *(first + (i - result) - 1))

  result is assigned the value of *first.

  adjacent_difference returns result + (last - first).

  result can be equal to first.  This allows you to place the results of
  applying adjacent_difference into the original sequence.

COMPLEXITY

  This algorithm performs exactly (last-first) - 1 applications of the
  default operation (-) or binary_op.

EXAMPLE

  //
  // adj_diff.cpp
  //
   #include<numeric>       //For adjacent_difference
   #include<vector>        //For vector
   #include<functional>    //For times
   #include <iostream.h>
  int main()
   {
     //
     //Initialize a vector of ints from an array
     //
    int arr[10] = {1,1,2,3,5,8,13,21,34,55};
    vector<int> v(arr,arr+10);
     //
     //Two uninitialized vectors for storing results
     //
    vector<int> diffs(10), prods(10);
     //
     //Calculate difference(s) using default operator (minus)
     //
    adjacent_difference(v.begin(),v.end(),diffs.begin());
     //
     //Calculate difference(s) using the times operator
     //
    adjacent_difference(v.begin(), v.end(), prods.begin(),
          times<int>());
     //
     //Output the results
     //
    cout << "For the vector: " << endl << "     ";
    copy(v.begin(),v.end(),
         ostream_iterator<int,char>(cout," "));
    cout << endl << endl;
    cout << "The differences between adjacent elements are: "
          << endl << "     ";
    copy(diffs.begin(),diffs.end(),
         ostream_iterator<int,char>(cout," "));
    cout << endl << endl;
    cout << "The products of adjacent elements are: "
          << endl << "     ";
    copy(prods.begin(),prods.end(),
         ostream_iterator<int,char>(cout," "));
    cout << endl;
    return 0;

  Output :
  For the vector:
      1 1 2 3 5 8 13 21 34 55
  The differences between adjacent elements are:
     1 0 1 1 2 3 5 8 13 21
  The products of adjacent elements are:
      1 1 2 6 15 40 104 273 714 1870

WARNING

  If your compiler does not support default template parameters then you need
  to always supply the Allocator template argument.  For instance you'll have
  to write:

  vector<int,allocator<int> >

  instead of:

  vector<int>

STANDARDS CONFORMANCE

  ANSI X3J16/ISO WG21 Joint C++ Committee



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