Standard Template Library Programmer's Guide

Insert a range of elements into a list .

list L;

L.push_front(3);

insert_iterator > ii(L, L.begin());

*ii++ = 0;

*ii++ = 1;

*ii++ = 2;

copy(L.begin(), L.end(), ostream_iterator(cout, " "));

// The values that are printed are 0 1 2 3.

Merge two sorted lists, inserting the resulting range into a set . Note that a set never contains duplicate elements.

int main() {

const int N = 6;

int A1[N] = {1, 3, 5, 7, 9, 11};

int A2[N] = {1, 2, 3, 4, 5, 6};

set result;

merge (A1, A1 + N, A2, A2 + N,

inserter(result, result.begin()));

copy(result.begin(), result.end(), ostream_iterator(cout, " "));

cout << endl;

// The output is "1 2 3 4 5 6 7 9 11".

}

Defined in the standard header iterator, and in the nonstandard backward-compatibility header iterator.h.

Output Iterator. An insert iterator's set of value types (as defined in the Output Iterator requirements) consists of a single type: Container::value_type .

• The template parameter Container is a model of Container.

• Container is variable-sized, as described in the Container requirements.

• Container has a two-argument insert member function. Specifically, if c is an object of type Container , p is an object of type Container::iterator and v is an object of type Container::value_type , then c.insert(p, v) must be a valid expression.

None.

These members are not defined in the Output Iterator requirements, but are specific to insert_iterator .

[1] Note the difference between assignment through a Container::iterator and assignment through an insert_iterator . If i is a valid Sequence::iterator , then it points to some particular element in the container; the expression *i = t replaces that element with t , and does not change the total number of elements in the container. If ii is a valid insert_iterator , however, then the expression *ii = t is equivalent, for some container c and some valid container::iterator j , to the expression c.insert(j, t) . That is, it does not overwrite any of c 's elements and it does change c 's size.

[2] Note how assignment through an insert_iterator is implemented. In general, unary operator* must be defined so that it returns a proxy object, where the proxy object defines operator= to perform the insert operation. In this case, for the sake of simplicity, the proxy object is the insert_iterator itself. That is, *i simply returns i , and *i = t is equivalent to i = t . You should not, however, rely on this behavior. It is an implementation detail, and it is not guaranteed to remain the same in future versions.

[3] This function exists solely for the sake of convenience: since it is a non-member function, the template parameters may be inferred and the type of the insert_iterator need not be declared explicitly. One easy way to reverse a range and insert it into a Sequence S , for example, is reverse_copy(first, last, inserter(S, S.begin())) .

front_insert_iterator, back_insert_iterator, Output Iterator, Sequence, Iterator overview

Categories: iterators, adaptors

Component type: type

Reverse_iterator is an iterator adaptor that enables backwards traversal of a range. Operator++ applied to an object of class reverse_iterator means the same thing as operator-- applied to an object of class RandomAccessIterator . There are two different reverse iterator adaptors: the class reverse_iterator has a template argument that is a Random Access Iterator, and the class reverse_bidirectional_iterator has a template argument that is a Bidirectional Iterator. [1]

template

void forw(const vector& V) {

vector::iterator first = V.begin();

vector::iterator last = V.end();

while (first != last) cout << *first++ << endl;

}

template

void rev(const vector& V) {

typedef reverse_iterator::iterator, T, vector::reference_type, vector::difference_type> reverse_iterator; [2]