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<H1>basic_string<charT, traits, Alloc></H1>
<Table CellPadding=0 CellSpacing=0 width=100%>
<TR>
<TD Align=left><Img src = "containers.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD>
<TD Align=right><Img src = "type.gif" Alt="" WIDTH = "194" HEIGHT = "39" ></TD>
</TR>
<TR>
<TD Align=left VAlign=top><b>Category</b>: containers</TD>
<TD Align=right VAlign=top><b>Component type</b>: type</TD>
</TR>
</Table>
<h3>Description</h3>
The <tt>basic_string</tt> class represents a <A href="Sequence.html">Sequence</A> of characters.
It contains all the usual operations of a <A href="Sequence.html">Sequence</A>, and, additionally,
it contains standard string operations such as search and concatenation.
<P>
The <tt>basic_string</tt> class is parameterized by character type, and by
that type's <A href="character_traits.html">Character Traits</A>. Most of the time, however, there is
no need to use the <tt>basic_string</tt> template directly. The types
<tt>string</tt> and <tt>wstring</tt> are typedefs for, respectively,
<tt>basic_string<char></tt> and <tt>basic_string<wchar_t></tt>.
<P>
Some of <tt>basic_string</tt>'s member functions use an unusual method of
specifying positions and ranges. In addition to the conventional
method using iterators, many of <tt>basic_string</tt>'s member functions use
a single value <tt>pos</tt> of type <tt>size_type</tt> to represent a position (in
which case the position is <tt>begin() + pos</tt>, and many of
<tt>basic_string</tt>'s member functions use two values, <tt>pos</tt> and <tt>n</tt>, to
represent a range. In that case <tt>pos</tt> is the beginning of the range
and <tt>n</tt> is its size. That is, the range is <tt>[begin() + pos, begin() +
pos + n)</tt>.
<P>
Note that the C++ standard does not specify the complexity of
<tt>basic_string</tt> operations. In this implementation, <tt>basic_string</tt>
has performance characteristics very similar to those of <tt><A href="Vector.html">vector</A></tt>:
access to a single character is <i>O(1</i>), while copy and concatenation
are <i>O(N</i>). By contrast, <tt><A href="Rope.html">rope</A></tt> has very different performance
characteristics: most <tt><A href="Rope.html">rope</A></tt> operations have logarithmic complexity.
<P>
Note also that, according to the C++ standard, <tt>basic_string</tt> has very
unusual iterator invalidation semantics. Iterators may be invalidated
by <tt>swap</tt>, <tt>reserve</tt>, <tt>insert</tt>, and <tt>erase</tt> (and by functions that are
equivalent to <tt>insert</tt> and/or <tt>erase</tt>, such as <tt>clear</tt>, <tt>resize</tt>,
<tt>append</tt>, and <tt>replace</tt>). Additionally, however, the first call to
<i>any</i> non-const member function, including the non-const version of
<tt>begin()</tt> or <tt>operator[]</tt>, may invalidate iterators. (The intent of
these iterator invalidation rules is to give implementors greater
freedom in implementation techniques.) In this implementation,
<tt>begin()</tt>, <tt>end()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>, <tt>operator[]</tt>, <tt>c_str()</tt>, and
<tt>data()</tt> do not invalidate iterators. In this implementation,
iterators are only invalidated by member functions that explicitly
change the string's contents.
<h3>Example</h3>
<pre>
int main() {
string s(10u, ' '); // Create a string of ten blanks.
const char* A = "this is a test";
s += A;
cout << "s = " << (s + '\n');
cout << "As a null-terminated sequence: " << s.c_str() << endl;
cout << "The sixteenth character is " << s[15] << endl;
reverse(s.begin(), s.end());
s.push_back('\n');
cout << s;
}
</pre>
<h3>Definition</h3>
Defined in <A href="string/index.htm">string</A>.
<h3>Template parameters</h3>
<Table border>
<TR>
<TH>
Parameter
</TH>
<TH>
Description
</TH>
<TH>
Default
</TH>
</TR>
<TR>
<TD VAlign=top>
<tt>charT</tt>
</TD>
<TD VAlign=top>
The string's value type: the type of character it contains.
</TD>
<TD VAlign=top>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>traits</tt>
</TD>
<TD VAlign=top>
The <A href="character_traits.html">Character Traits</A> type, which encapsulates basic character
operations.
</TD>
<TD VAlign=top>
<tt>char_traits<charT></tt>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>Alloc</tt>
</TD>
<TD VAlign=top>
The string's allocator, used for internal memory management.
</TD>
<TD VAlign=top>
<tt>alloc</tt>
</TD>
</tr>
</table>
<h3>Model of</h3>
<A href="RandomAccessContainer.html">Random Access Container</A>,
<A href="Sequence.html">Sequence</A>.
<h3>Type requirements</h3>
In addition to the type requirements imposed by
<A href="RandomAccessContainer.html">Random Access Container</A> and <A href="Sequence.html" tppabs="http://www.sgi.com/Technology/STL/Sequence.shtml">Sequence</A>:
<UL>
<LI>
<tt>charT</tt> is a POD ("plain 'ol data") type.
<LI>
<tt>traits</tt> is a <A href="character_traits.html">Character Traits</A> type whose value type is
<tt>charT</tt>
</UL>
<h3>Public base classes</h3>
None.
<h3>Members</h3>
<Table border>
<TR>
<TH>
Member
</TH>
<TH>
Where defined
</TH>
<TH>
Description
</TH>
</TR>
<TR>
<TD VAlign=top>
<tt>value_type</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
The type of object, <tt>CharT</tt>, stored in the string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>pointer</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Pointer to <tt>CharT</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>reference</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Reference to <tt>CharT</tt>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_reference</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Const reference to <tt>CharT</tt>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>size_type</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
An unsigned integral type.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>difference_type</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
A signed integral type.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>static const size_type npos</tt>
</TD>
<TD VAlign=top>
<tt>basic_string</tt>
</TD>
<TD VAlign=top>
The largest possible value of type <tt>size_type</tt>. That is,
<tt>size_type(-1)</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>iterator</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Iterator used to iterate through a string. A <tt>basic_string</tt> supplies
<A href="RandomAccessIterator.html">Random Access Iterators</A>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_iterator</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Const iterator used to iterate through a string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>reverse_iterator</tt>
</TD>
<TD VAlign=top>
<A href="ReversibleContainer.html">Reversible Container</A>
</TD>
<TD VAlign=top>
Iterator used to iterate backwards through a string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_reverse_iterator</tt>
</TD>
<TD VAlign=top>
<A href="ReversibleContainer.html">Reversible Container</A>
</TD>
<TD VAlign=top>
Const iterator used to iterate backwards through a string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>iterator begin()</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns an <tt>iterator</tt> pointing to the beginning of the string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>iterator end()</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns an <tt>iterator</tt> pointing to the end of the string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_iterator begin() const</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns a <tt>const_iterator</tt> pointing to the beginning of the string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_iterator end() const</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns a <tt>const_iterator</tt> pointing to the end of the string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>reverse_iterator rbegin()</tt>
</TD>
<TD VAlign=top>
<A href="ReversibleContainer.html">Reversible Container</A>
</TD>
<TD VAlign=top>
Returns a <tt>reverse_iterator</tt> pointing to the beginning of the
reversed string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>reverse_iterator rend()</tt>
</TD>
<TD VAlign=top>
<A href="ReversibleContainer.html">Reversible Container</A>
</TD>
<TD VAlign=top>
Returns a <tt>reverse_iterator</tt> pointing to the end of the
reversed string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_reverse_iterator rbegin() const</tt>
</TD>
<TD VAlign=top>
<A href="ReversibleContainer.html">Reversible Container</A>
</TD>
<TD VAlign=top>
Returns a <tt>const_reverse_iterator</tt> pointing to the beginning of the
reversed string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_reverse_iterator rend() const</tt>
</TD>
<TD VAlign=top>
<A href="ReversibleContainer.html">Reversible Container</A>
</TD>
<TD VAlign=top>
Returns a <tt>const_reverse_iterator</tt> pointing to the end of the
reversed string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>size_type size() const</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns the size of the string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>size_type length() const</tt>
</TD>
<TD VAlign=top>
<tt>basic_string</tt>
</TD>
<TD VAlign=top>
Synonym for <tt>size()</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>size_type max_size() const</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns the largest possible size of the string.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>size_type capacity() const</tt>
</TD>
<TD VAlign=top>
<tt>basic_string</tt>
</TD>
<TD VAlign=top>
See below.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>bool empty() const</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
<tt>true</tt> if the string's size is <tt>0</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>reference operator[](size_type n)</tt>
</TD>
<TD VAlign=top>
<A href="RandomAccessContainer.html">Random Access Container</A>
</TD>
<TD VAlign=top>
Returns the <tt>n</tt>'th character.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_reference operator[](size_type n) const</tt>
</TD>
<TD VAlign=top>
<A href="RandomAccessContainer.html">Random Access Container</A>
</TD>
<TD VAlign=top>
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