vector (3C++std) - Tru64 UNIX
Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc.
NAME
vector - Sequence that supports random access iterators.
This page describes the ANSI vector class. If you would like information
on the pre-ANSI vector class, use the command:
man 3C++ vector or man vector.3C++
SYNOPSIS
#include <vector>
template <class T, class Allocator = allocator<T> >
class vector ;
DESCRIPTION
vector<T, Allocator> is a type of sequence that supports random access
iterators. In addition, it supports amortized constant time insert and
erase operations at the end. Insert and erase in the middle take linear
time. Storage management is handled automatically. In vector, iterator is
a random access iterator referring to T. const_iterator is a constant
random access iterator that returns a const T& when being dereferenced. A
constructor for iterator and const_iterator is guaranteed. size_type is an
unsigned integral type. difference_type is a signed integral type.
Any type used for the template parameter T must provide the following
(where T is the type, t is a value of T and u is a const value of T):
Default constructor T()
Copy constructors T(t) and T(u)
Destructor t.~T()
Address of &t and &u yielding T* and
const T* respectively
Assignment t = a where a is a
(possibly const) value of T
SPECIAL CASE
Vectors of bit values (boolean 1/0 values) are handled as a special case by
the standard library, so that they can be efficiently packed several
elements to a word. The operations for a boolean vector, vector<bool>, are
a superset of those for an ordinary vector, only the implementation is more
efficient.
Two member functions are available to the boolean vector data type. One
is flip(), which inverts all the bits of the vector. Boolean vectors also
return as reference an internal value that also supports the flip() member
function. The other vector<bool>-specific member function is a second form
of the swap() function
INTERFACE
template <class T, class Allocator = allocator<T> >
class vector {
public:
// Types
typedef T value_type;
typedef Allocator allocator_type;
typename reference;
typename const_reference;
typename iterator;
typename const_iterator;
typename size_type;
typename difference_type;
typename reverse_iterator;
typename const_reverse_iterator;
// Construct/Copy/Destroy
explicit vector (const Allocator& = Allocator());
explicit vector (size_type, const Allocator& = Allocator ());
vector (size_type, const T&, const Allocator& = Allocator());
vector (const vector<T, Allocator>&);
template <class InputIterator>
vector (InputIterator, InputIterator,
const Allocator& = Allocator ());
~vector ();
vector<T,Allocator>& operator= (const vector<T, Allocator>&);
template <class InputIterator>
void assign (InputIterator first, InputIterator last);
template <class Size, class TT>
void assign (Size n);
template <class Size, class TT>
void assign (Size n, const TT&);
allocator_type get_allocator () const;
// Iterators
iterator begin ();
const_iterator begin () const;
iterator end ();
const_iterator end () const;
reverse_iterator rbegin ();
const_reverse_iterator rbegin () const;
reverse_iterator rend ();
const_reverse_iterator rend () const;
// Capacity
size_type size () const;
size_type max_size () const;
void resize (size_type);
void resize (size_type, T);
size_type capacity () const;
bool empty () const;
void reserve (size_type);
// Element Access
reference operator[] (size_type);
const_reference operator[] (size_type) const;
reference at (size_type);
const_reference at (size_type) const;
reference front ();
const_reference front () const;
reference back ();
const_reference back () const;
// Modifiers
void push_back (const T&);
void pop_back ();
iterator insert (iterator);
iterator insert (iterator, const T&);
void insert (iterator, size_type, const T&);
template <class InputIterator>
void insert (iterator, InputIterator, InputIterator);
iterator erase (iterator);
iterator erase (iterator, iterator);
void swap (vector<T, Allocator>&);
};
// Non-member Operators
template <class T>
bool operator== (const vector<T,Allocator>&,
const vector <T,Allocator>&);
template <class T>
bool operator!= (const vector<T,Allocator>&,
const vector <T,Allocator>&);
template <class T>
bool operator< (const vector<T,Allocator>&,
const vector<T,Allocator>&);
template <class T>
bool operator> (const vector<T,Allocator>&,
const vector<T,Allocator>&);
template <class T>
bool operator<= (const vector<T,Allocator>&,
const vector<T,Allocator>&);
template <class T>
bool operator>= (const vector<T,Allocator>&,
const vector<T,Allocator>&);
// Specialized Algorithms
template <class T, class Allocator>
void swap (const vector<T,Allocator>&, const vector<T,Allocator>&);
CONSTRUCTORS AND DESTRUCTORS
explicit vector(const Allocator& alloc = Allocator());
The default constructor. Creates a vector of length zero. The vector
will use the allocator alloc for all storage management.
explicit vector(size_type n,
const Allocator& alloc = Allocator());
Creates a vector of length n, containing n copies of the
default value for type T. Requires that T have a default
constructor. The vector will use the allocator alloc
for all storage management.
vector(size_type n, const T& value,
const Allocator& alloc = Allocator());
Creates a vector of length n, containing n copies of value. The
vector will use the allocator alloc for all storage management.
vector(const vector<T, Allocator>& x);
Creates a copy of x.
template <class InputIterator>
vector(InputIterator first, InputIterator last,
const Allocator& alloc = Allocator());
Creates a vector of length last - first, filled with all values
obtained by dereferencing the InputIterators on the range [first,
last). The vector will use the allocator alloc for all storage
management.
~vector();
The destructor. Releases any allocated memory for this vector.
ITERATORS
iterator
begin();
Returns a random access iterator that points to the first element.
const_iterator
begin() const;
Returns a random access const_iterator that points to the first element.
iterator
end();
Returns a random access iterator that points to the past-the-end value.
const_iterator
end() const;
Returns a random access const_iterator that points to the past-the-end
value.
reverse_iterator
rbegin();
Returns a random access reverse_iterator that points to the past-the-end
value.
const_reverse_iterator
rbegin() const;
Returns a random access const_reverse_iterator that points to the past-
the-end value.
reverse_iterator
rend();
Returns a random access reverse_iterator that points to the first
element.
const_reverse_iterator
rend() const;
Returns a random access const_reverse_iterator that points to the first
element.
ASSIGNMENT OPERATOR
vector<T, Allocator>&
operator=(const vector<T, Allocator>& x);
Erases all elements in self then inserts into self a copy of each
element in x. Returns a reference to self.
ALLOCATOR
allocator_type
get_allocator() const;
Returns a copy of the allocator used by self for storage management.
REFERENCE OPERATORS
reference
operator[](size_type n);
Returns a reference to element n of self. The result can be used as an
lvalue. The index n must be between 0 and the size less one.
const_reference
operator[](size_type n) const;
Returns a constant reference to element n of self. The index n must be
between 0 and the size less one.
MEMBER FUNCTIONS
template <class InputIterator>
void
assign(InputIterator first, InputIterator last);
Erases all elements contained in self, then inserts new elements from
the range [first, last).
template <class Size, class T>
void
assign(Size n, const T& t);
Erases all elements contained in self, then inserts n instances of the
default value of type T.
template <class Size, class T>
void
assign(Size n, const T& t);
Erases all elements contained in self, then inserts n instances of the
value of t.
reference
at(size_type n);
Returns a reference to element n of self. The result can be used as an
lvalue. The index n must be between 0 and the size less one.
const_reference
at(size_type) const;
Returns a constant reference to element n of self. The index n must be
between 0 and the size less one.
reference
back();
Returns a reference to the last element.
const_reference
back() const;
Returns a constant reference to the last element.
size_type
capacity() const;
Returns the size of the allocated storage, as the number of elements
that can be stored.
void
clear() ;
Deletes all elements from the vector.
bool
empty() const;
Returns true if the size is zero.
iterator
erase(iterator position);
Deletes the vector element pointed to by the iterator position. Returns
an iterator pointing to the element following the deleted element, or
end() if the deleted element was the last one in this vector.
iterator
erase(iterator first, iterator last);
Deletes the vector elements in the range (first, last). Returns an
iterator pointing to the element following the last deleted element, or
end() if there were no elements in the deleted range.
void
flip();
Flips all the bits in the vector. This member function is only defined
for vector<bool>.
reference
front();
Returns a reference to the first element.
const_reference
front() const;
Returns a constant reference to the first element.
iterator
insert(iterator position);
Inserts x before position. The return value points to the inserted x.
iterator
insert(iterator position, const T& x);
Inserts x before position. The return value points to the inserted x.
void
insert(iterator position, size_type n, const T& x);
Inserts n copies of x before position.
template <class InputIterator>
void
insert(iterator position, InputIterator first,
InputIterator last);
Inserts copies of the elements in the range [first, last] before
position.
size_type
max_size() const;
Returns size() of the largest possible vector.
void
pop_back();
Removes the last element of self.
void
push_back(const T& x);
Inserts a copy of x to the end of self.
void
reserve(size_type n);
Increases the capacity of self in anticipation of adding new elements.
reserve itself does not add any new elements. After a call to reserve,
capacity() is greater than or equal to n and subsequent insertions will
not cause a reallocation until the size of the vector exceeds n.
Reallocation does not occur if n is less than capacity(). If
reallocation does occur, then all iterators and references pointing to
elements in the vector are invalidated. reserve takes at most linear
time in the size of self.
void
resize(size_type sz);
Alters the size of self. If the new size (sz) is greater than the
current size, then sz-size() instances of the default value of type T
are inserted at the end of the vector. If the new size is smaller than
the current capacity, then the vector is truncated by erasing size()-sz
elements off the end. If sz is equal to capacity then no action is
taken.
void
resize(size_type sz, T c);
Alters the size of self. If the new size (sz) is greater than the
current size, then sz-size() c's are inserted at the end of the vector.
If the new size is smaller than the current capacity, then the vector is
truncated by erasing size()-sz elements off the end. If sz is equal to
capacity then no action is taken.
size_type
size() const;
Returns the number of elements.
void
swap(vector<T, Allocator>& x);
Exchanges self with x, by swapping all elements.
void
swap(reference x, reference y);
Swaps the values of x and y. This is a member function of vector<bool>
only.
NON-MEMBER OPERATORS
template <class T, class Allocator>
bool operator==(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns true if x is the same as y.
template <class T, class Allocator>
bool operator!=(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns !(x==y).
template <class T>
bool operator<(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns true if the elements contained in x are
lexicographically less than the elements contained in y.
template <class T>
bool operator>(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns y < x.
template <class T>
bool operator<=(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns !(y < x).
template <class T>
bool operator>=(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns !(x < y).
SPECIALIZED ALGORITHMS
template <class T, class Allocator>
void swap(vector <T, Allocator>& a, vector <T, Allocator>& b);
Efficiently swaps the contents of a and b.
EXAMPLE
//
// vector.cpp
//
#include <vector>
#include <iostream.h>
ostream& operator<< (ostream& out,
const vector<int, allocator>& v)
{
copy(v.begin(), v.end(), ostream_iterator<int,char>(out," "));
return out;
}
int main(void)
{
// create a vector of doubles
vector<int> vi;
int i;
for(i = 0; i < 10; ++i) {
// insert values before the beginning
vi.insert(vi.begin(), i);
}
// print out the vector
cout << vi << endl;
// now let's erase half of the elements
int half = vi.size() >> 1;
for(i = 0; i < half; ++i) {
vi.erase(vi.begin());
}
// print ir out again
cout << vi << endl;
return 0;
}
Output :
9 8 7 6 5 4 3 2 1 0
4 3 2 1 0
WARNINGS
Member function templates are used in all containers provided by the
Standard C++ Library. An example of this feature is the constructor for
vector<T, Allocator> that takes two templated iterators:
template <class InputIterator>
vector (InputIterator, InputIterator,
const Allocator = Allocator());
vector also has an insert function of this type. These functions, when not
restricted by compiler limitations, allow you to use any type of input
iterator as arguments. For compilers that do not support this feature we
provide substitute functions that allow you to use an iterator obtained
from the same type of container as the one you are constructing (or calling
a member function on), or you can use a pointer to the type of element you
have in the container.
For example, if your compiler does not support member function templates
you can construct a vector in the following two ways:
int intarray[10];
vector<int> first_vector(intarray, intarray + 10);
vector<int> second_vector(first_vector.begin(),
first_vector.end());
but not this way:
vector<long>
long_vector(first_vector.begin(),first_vector.end());
since the long_vector and first_vector are not the same type.
Additionally, if your compiler does not support default template
parameters, you will need to supply the Allocator template argument. For
instance, you will need to write :
vector<int, allocator<int> >
instead of :
vector<int>
SEE ALSO
allocator, Containers, Iterators, lexicographical_compare
STANDARDS CONFORMANCE
ANSI X3J16/ISO WG21 Joint C++ Committee
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