remove (3C++std) - Tru64 UNIX
Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc. NAME
remove - Move desired elements to the front of a container, and return an
iterator that describes where the sequence of desired elements ends.
SYNOPSIS
#include <algorithm>
template <class ForwardIterator, class T>
ForwardIterator
remove (ForwardIterator first,
ForwardIterator last,
const T& value);
DESCRIPTION
The remove algorithm eliminates all the elements referred to by iterator i
in the range [first, last) for which the following condition holds: *i
== value. remove returns an iterator that designates the end of the
resulting range. remove is stable, that is, the relative order of the
elements that are not removed is the same as their relative order in the
original range.
remove does not actually reduce the size of the sequence. It actually
operates by: 1) copying the values that are to be retained to the front of
the sequence, and 2) returning an iterator that describes where the
sequence of retained values ends. Elements that are after this iterator
are simply the original sequence values, left unchanged. Here's a simple
example:
Say we want to remove all values of "2" from the following sequence:
354621271
Applying the remove algorithm results in the following sequence:
3546171|XX
The vertical bar represents the position of the iterator returned by
remove. Note that the elements to the left of the vertical bar are the
original sequence with the "2's" removed.
If you want to actually delete items from the container, use the following
technique:
container.erase(remove(first,last,value),container.end());
COMPLEXITY
Exactly last1 - first1 applications of the corresponding predicate are
done.
EXAMPLE
//
// remove.cpp
//
#include <algorithm>
#include <vector>
#include <iterator>
#include <iostream.h>
template<class Arg>
struct all_true : public unary_function<Arg, bool>
{
bool operator()(const Arg& x){ return 1; }
};
int main ()
{
int arr[10] = {1,2,3,4,5,6,7,8,9,10};
vector<int> v(arr, arr+10);
copy(v.begin(),v.end(),ostream_iterator<int,char>(cout," "));
cout << endl << endl;
// remove the 7
vector<int>::iterator result =
remove(v.begin(), v.end(), 7);
// delete dangling elements from the vector
v.erase(result, v.end());
copy(v.begin(),v.end(),ostream_iterator<int,char>(cout," "));
cout << endl << endl;
// remove everything beyond the fourth element
result = remove_if(v.begin()+4,
v.begin()+8, all_true<int>());
// delete dangling elements
v.erase(result, v.end());
copy(v.begin(),v.end(),ostream_iterator<int,char>(cout," "));
cout << endl << endl;
return 0;
}
Output :
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 8 9 10
1 2 3 4
1 2 4
WARNING
If your compiler does not support default template parameters, you need to
always supply the Allocator template argument. For instance, you will need
to write :
vector<int, allocator<int> >
instead of :
vector<int>
SEE ALSO
remove_if, remove_copy, remove_copy_if
STANDARDS CONFORMANCE
ANSI X3J16/ISO WG21 Joint C++ Committee
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