Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.
NAME
remove
- Moves desired elements to the front of a container, and
returns 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 fol-
lowing condition holds: *i == value. remove returns an
iterator that points to the end of the resulting range.
remove is stable, which means that 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: 1) copies the values that are to be retained to
the front of the sequence, and 2) returns an iterator that
describes where the sequence of retained values ends. Ele-
ments that follow 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 "2s"
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>
using namespace std;
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;
}
Program 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
WARNINGS
If your compiler does not support default template parame-
ters, you always need to supply the Allocator template argu-
ment. For instance, you need to write:
vector<int, allocator<int> >
instead of:
vector<int>
If your compiler does not support namespaces, then you do
not need the using declaration for std.
SEE ALSO
remove_if, remove_copy, remove_copy_if