set_difference (3C++std) - Tru64 UNIX
Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc. NAME
set_difference - Basic set operation for sorted sequences.
SYNOPSIS
#include <algorithm>
template <class InputIterator1, class InputIterator2,
class OutputIterator>
OutputIterator
set_difference (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
template <class InputIterator1, class InputIterator2,
class OutputIterator, class Compare>
OutputIterator
set_difference (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
DESCRIPTION
The set_difference algorithm constructs a sorted difference that includes
copies of the elements that are present in the range [first1, last1) but
are not present in the range [first2, last2). It returns the end of the
constructed range.
As an example, assume we have the following two sets:
1 2 3 4 5
and
3 4 5 6 7
The result of applying set_difference is the set:
1 2
The result of set_difference is undefined if the result range overlaps with
either of the original ranges.
set_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_symetric_difference algorithm to return a result that contains
all elements that are not in common between the two sets.
COMPLEXITY
At most ((last1 - first1) + (last2 - first2)) * 2 -1 comparisons are
performed.
EXAMPLE
//
// set_diff.cpp
//
#include <algorithm>
#include <set>
#include <iostream.h>
int main()
{
//Initialize some sets
int a1[10] = {1,2,3,4,5,6,7,8,9,10};
int a2[6] = {2,4,6,8,10,12};
set<int, less<int> > all(a1, a1+10), even(a2, a2+6),
odd;
//Create an insert_iterator for odd
insert_iterator<set<int, less<int> > >
odd_ins(odd, odd.begin());
//Demonstrate set_difference
cout << "The result of:" << endl << "{";
copy(all.begin(),all.end(),
ostream_iterator<int,char>(cout," "));
cout << "} - {";
copy(even.begin(),even.end(),
ostream_iterator<int,char>(cout," "));
cout << "} =" << endl << "{";
set_difference(all.begin(), all.end(),
even.begin(), even.end(), odd_ins);
copy(odd.begin(),odd.end(),
ostream_iterator<int,char>(cout," "));
cout << "}" << endl << endl;
return 0;
}
Output :
The result of:
{1 2 3 4 5 6 7 8 9 10 } - {2 4 6 8 10 12 } =
{1 3 5 7 9 }
WARNING
If your compiler does not support default template parameters, then you
need to always supply the Compare template argument and the Allocator
template argument. For instance, you will need to write :
set<int, less<int> allocator<int> >
instead of :
set<int>
SEE ALSO
includes, set, set_union, set_intersection, set_symmetric_difference
STANDARDS CONFORMANCE
ANSI X3J16/ISO WG21 Joint C++ Committee
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