front_insert_iterator<FrontInsertionSequence> front_insert_iterator<FrontInsertionSequence> Categories: iterators, adaptors Component type: type Description Front_insert_iterator is an iterator adaptor that functions as an Output Iterator: assignment through a front_insert_iterator inserts an object before the first element of a Front Insertion Sequence. [1] [2] Example list<int> L; L.push_front(3); front_insert_iterator<list<int> > ii(L); *ii++ = 0; *ii++ = 1; *ii++ = 2; copy(L.begin(), L.end(), ostream_iterator<int>(cout, " ")); // The values that are printed are 2 1 0 3 Definition Defined in the standard header iterator, and in the nonstandard backward-compatibility header iterator.h. Template parameters Parameter Description Default FrontInsertionSequence The type of Front Insertion Sequence into which values will be inserted.   Model of Output Iterator. A front insert iterator's set of value types (as defined in the Output Iterator requirements) consists of a single type: FrontInsertionSequence::value_type. Type requirements The template parameter FrontInsertionSequence must be a Front Insertion Sequence. Public base classes None. Members Member Where defined Description front_insert_iterator(FrontInsertionSequence&) front_insert_iterator See below. front_insert_iterator(const front_insert_iterator&) Trivial Iterator The copy constructor front_insert_iterator& operator=(const front_insert_iterator&) Trivial Iterator The assignment operator front_insert_iterator& operator*() Output Iterator Used to implement the output iterator expression *i = x. [3] front_insert_iterator& operator=(const FrontInsertionSequence::value_type&) Output Iterator Used to implement the output iterator expression *i = x. [3] front_insert_iterator& operator++() Output Iterator Preincrement. front_insert_iterator& operator++(int) Output Iterator Postincrement. output_iterator_tag iterator_category(const front_insert_iterator&) iterator tags Returns the iterator's category. This is a global function, not a member. template<class FrontInsertionSequence> front_insert_iterator<FrontInsertionSequence> front_inserter(FrontInsertionSequence& S) front_insert_iterator See below. New members. These members are not defined in the Output Iterator requirements, but are specific to front_insert_iterator. Member Description front_insert_iterator(FrontInsertionSequence& S) Constructs a front_insert_iterator that inserts objects before the first element of S. template<class FrontInsertionSequence> front_insert_iterator<FrontInsertionSequence> front_inserter(FrontInsertionSequence& S); Equivalent to front_insert_iterator<FrontInsertionSequence>(S). [4] This is a global function, not a member function. Notes [1] Note the difference between assignment through a FrontInsertionSequence::iterator and assignment through an front_insert_iterator<FrontInsertionSequence>. If i is a valid FrontInsertionSequence::iterator, then it points to some particular element in the front insertion sequence; the expression *i = t replaces that element with t, and does not change the total number of elements in the sequence. If ii is a valid front_insert_iterator<FrontInsertionSequence>, however, then the expression *ii = t is equivalent, for some FrontInsertionSequence seq, to the expression seq.push_front(t). That is, it does not overwrite any of seq's elements and it does change seq's size. [2] Note the difference between a front_insert_iterator and an insert_iterator. It may seem that a front_insert_iterator is the same as an insert_iterator constructed with an insertion point that is the beginning of a sequence. In fact, though, there is a very important difference: every assignment through a front_insert_iterator corresponds to an insertion before the first element of the sequence. If you are inserting elements at the beginning of a sequence using an insert_iterator, then the elements will appear in the order in which they were inserted. If, however, you are inserting elements at the beginning of a sequence using a front_insert_iterator, then the elements will appear in the reverse of the order in which they were inserted. [3] Note how assignment through an front_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 front_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. [4] 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 front_insert_iterator need not be declared explicitly. One easy way to reverse a range and insert it at the beginning of a Front Insertion Sequence S, for example, is copy(first, last, front_inserter(S)). See also insert_iterator, back_insert_iterator, Output Iterator, Sequence, Front Insertion Sequence, Iterator overview Copyright © 1999 Silicon Graphics, Inc. All Rights Reserved. TrademarkInformation