DescriptionFront_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.  
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
DefinitionDefined in the standard header iterator, and in the nonstandard backward-compatibility header iterator.h.
Model ofOutput 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 requirementsThe template parameter FrontInsertionSequence must be a Front Insertion Sequence.
Public base classesNone.
New members.These members are not defined in the Output Iterator requirements, but are specific to front_insert_iterator.
 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.
 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.
 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.
 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 alsoinsert_iterator, back_insert_iterator, Output Iterator, Sequence, Front Insertion Sequence, Iterator overview
Copyright © 1999 Silicon Graphics, Inc. All Rights Reserved. TrademarkInformation