# Man Page set_symmetric_difference.3

```
Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.

```

## NAME

```     set_symmetric_difference

- A basic set operation for constructing a sorted symmetric
difference.

```

## SYNOPSIS

```     #include <algorithm>
template <class InputIterator1, class InputIterator2,
class OutputIterator>
OutputIterator
set_symmetric_difference (InputIterator1 first1,
InputIterator1 last1,
InputIterator2 first2,
InputIterator2 last2,
OutputIterator result);
template <class InputIterator1, class InputIterator2,
class OutputIterator, class Compare>
OutputIterator
set_symmetric_difference (InputIterator1 first1,
InputIterator1 last1,
InputIterator2 first2,
InputIterator2 last2,
OutputIterator result,
Compare comp);

```

## DESCRIPTION

```     set_symmetric_difference  constructs  a   sorted   symmetric
difference  of  the elements from the two ranges. This means
that the constructed range includes copies of  the  elements
that  are  present  in  the  range  [first1, last1) (but not
present in the range [first2, last2)) and copies of the ele-
ments that are present in the range [first2, last2) (but not
in the range [first1, last1)). It returns  the  end  of  the
constructed range.

For example, suppose we have two sets:

1 2 3 4 5

and

3 4 5 6 7

The set_symmetric_difference of these two sets is:

1 2 6 7

The result of set_symmetric_difference is undefined  if  the
result range overlaps with either of the original ranges.

set_symmetric_difference assumes that the ranges are  sorted
using  the default comparison operator less than (<), unless
an alternative comparison operator (comp) is provided.

Use  the  set_symmetric_difference  algorithm  to  return  a
result  that includes elements that are present in the first
set and not in the second.

```

## COMPLEXITY

```     At most ((last1 - first1) + (last2 - first2)) *  2  -1  com-
parisons are performed.

```

## EXAMPLE

```     //
// set_s_di.cpp
//
#include<algorithm>
#include<set>
#include <istream.h>
using namespace std;

int main()
{

//Initialize some sets
int a1[] = {1,3,5,7,9,11};
int a3[] = {3,5,7,8};
set<int, less<int> > odd(a1+0,a1+6), result,
small(a3+0,a3+4);
//Create an insert_iterator for result
insert_iterator<set<int, less<int> > >
res_ins(result, result.begin());
//Demonstrate set_symmetric_difference
cout << "The symmetric difference of:" << endl << "{";
copy(small.begin(),small.end(),
ostream_iterator<int,char>(cout," "));
cout << "} with {";
copy(odd.begin(),odd.end(),
ostream_iterator<int,char>(cout," "));
cout << "} =" << endl << "{";
set_symmetric_difference(small.begin(), small.end(),
odd.begin(), odd.end(), res_ins);
copy(result.begin(),result.end(),
ostream_iterator<int,char>(cout," "));
cout << "}" << endl << endl;
return 0;
}

Program Output

The symmetric difference of:
{3 5 7 8 } with {1 3 5 7 9 11 } =
{1 8 9 11 }

```

## WARNINGS

```     If your compiler does not support default  template  parame-
ters,  then  you  always need to supply the Compare template
argument and the Allocator template argument. For  instance,
you need to write:

set<int, less<int>, allocator<int> >

set<int>

If your compiler does not support namespaces,  then  you  do
not need the using declaration for std.

```

```     includes, set, set_union, set_intersection, set_difference