______________________________________________________________________

  21   Strings library                           [lib.strings]

  ______________________________________________________________________

1 This clause describes components for manipulating sequences of  "char­
  acters,"  where  characters may be of type char, wchar_t, or of a type
  defined in a C++ program.

2 The following subclauses describe string classes, and  null-terminated
  sequence utilities, as summarized in Table 1:

                     Table 1--Strings library summary

     +---------------------------------------------------------------+
     |                    Subclause                        Header(s) |
     +---------------------------------------------------------------+
     |_lib.string.classes_ String classes                  <string>  |
     +---------------------------------------------------------------+
     |                                                     <cctype>  |
     |                                                     <cwctype> |
     |_lib.c.strings_ Null-terminated sequence utilities   <cstring> |
     |                                                     <cwchar>  |
     |                                                     <cstdlib> |
     +---------------------------------------------------------------+

  21.1  String classes                              [lib.string.classes]

  Header <string> synopsis

  #include <memory>       // for allocator

  namespace std {
  // subclause _lib.template.string_, basic_string:
    template<class charT> struct string_char_traits;
    template<class charT, class traits = string_char_traits<charT>,
             class Allocator = allocator> class basic_string;

    template<class charT, class traits, class Allocator>
      basic_string<charT,traits,Allocator>
        operator+(const basic_string<charT,traits,Allocator>& lhs,
                  const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      basic_string<charT,traits,Allocator>
        operator+(const charT* lhs,
                  const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      basic_string<charT,traits,Allocator>
        operator+(charT lhs, const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      basic_string<charT,traits,Allocator>
        operator+(const basic_string<charT,traits,Allocator>& lhs,
                  const_pointer rhs);
    template<class charT, class traits, class Allocator>
      basic_string<charT,traits,Allocator>
        operator+(const basic_string<charT,traits,Allocator>& lhs, charT rhs);
    template<class charT, class traits, class Allocator>
      bool operator==(const basic_string<charT,traits,Allocator>& lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      bool operator==(const charT* lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      bool operator==(const basic_string<charT,traits,Allocator>& lhs,
                      const charT* rhs);
    template<class charT, class traits, class Allocator>
      bool operator!=(const basic_string<charT,traits,Allocator>& lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      bool operator!=(const charT* lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      bool operator!=(const basic_string<charT,traits,Allocator>& lhs,
                      const charT* rhs);
    template<class charT, class traits, class Allocator>
      bool operator< (const basic_string<charT,traits,Allocator>& lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      bool operator< (const basic_string<charT,traits,Allocator>& lhs,
                      const charT* rhs);
    template<class charT, class traits, class Allocator>
      bool operator< (const charT* lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      bool operator> (const basic_string<charT,traits,Allocator>& lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      bool operator> (const basic_string<charT,traits,Allocator>& lhs,
                      const charT* rhs);
    template<class charT, class traits, class Allocator>
      bool operator> (const charT* lhs,
                      const basic_string<charT,traits,Allocator>& rhs);

    template<class charT, class traits, class Allocator>
      bool operator<=(const basic_string<charT,traits,Allocator>& lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      bool operator<=(const basic_string<charT,traits,Allocator>& lhs,
                      const charT* rhs);
    template<class charT, class traits, class Allocator>
      bool operator<=(const charT* lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      bool operator>=(const basic_string<charT,traits,Allocator>& lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      bool operator>=(const basic_string<charT,traits,Allocator>& lhs,
                      const charT* rhs);
    template<class charT, class traits, class Allocator>
      bool operator>=(const charT* lhs,
                      const basic_string<charT,traits,Allocator>& rhs);
    template<class charT, class traits, class Allocator>
      basic_istream<charT>&
        operator>>(basic_istream<charT>& is,
                   basic_string<charT,traits,Allocator>& str);
    template<class charT, class traits, class Allocator>
      basic_ostream<charT>&
        operator<<(basic_ostream<charT>& os,
                   const basic_string<charT,traits,Allocator>& str);
    template<class charT, class IS_traits, class STR_traits, class STR_Alloc>
      basic_istream<charT,IS_traits>&
        getline(basic_istream<charT,IS_traits>& is,
                basic_string<charT,STR_traits,STR_Alloc>& str,
                charT delim = IS_traits::newline() );
  // subclause _lib.string_, string:
    struct string_char_traits<char>;
    typedef basic_string<char> string;
  // subclause _lib.wstring_, wstring:
    struct string_char_traits<wchar_t>;
    typedef basic_string<wchar_t> wstring;
  }

1 In  this  subclause,  we  call  the  basic character types "char-like"
  types, and also  call  the  objects  of  char-like  types  "char-like"
  objects or simply "character"s.

2 The  header  <string>  defines  a  basic string class template and its
  traits that can handle all "char-like" template arguments with several
  function  signatures  for  manipulating  varying-length  sequences  of
  "char-like" objects.

3 The header <string> also defines two specific template classes  string
  and wstring and their special traits.

  21.1.1  Template class basic_string              [lib.template.string]

  21.1.1.1  Template class                      [lib.string.char.traits]
       string_char_traits
  namespace std {
    template<class charT> struct string_char_traits {
      typedef charT char_type; // for users to acquire the basic character type
      static void assign(char_type& c1, const char_type& c2)
      static bool eq(const char_type& c1, const char_type& c2)
      static bool ne(const char_type& c1, const char_type& c2)
      static bool lt(const char_type& c1, const char_type& c2)
      static char_type eos(); // the null character
      static basic_istream<charT>& char_in (basic_istream<charT>& is, char_type& a);
      static basic_ostream<charT>& char_out(basic_ostream<charT>& os, char_type a);
      static bool is_del(char_type a); // characteristic function for delimiters
      // speed-up functions
      static int compare(const char_type* s1, const char_type* s2, size_t n);
      static size_t length(const char_type* s);
      static char_type* copy(char_type* s1, const char_type* s2, size_t n);
    };
  }

  21.1.1.2  string_char_traits          [lib.string.char.traits.members]
       members

1 Default definitions.

  static void assign(char_type& c1, const char_type& c2)

  Effects:
    Assigns c2 to c1.

  static bool eq(const char_type& c1, const char_type& c2)

  Returns
    c1 == c2

  static bool ne(const char_type& c1, const char_type& c2)

  Returns:
    !(c1 == c2)

  static bool lt(const char_type& c1, const char_type& c2)

  Returns:
    c1 < c2

  static char_type eos();

  Returns
    The null character, char_type()

  static basic_istream<charT>&
    char_in(basic_istream<charT>& is, char_type& a);

  Effects:
    Extracts a charT object.
  Returns:
    is >> a

  static basic_ostream<charT>&
    char_out(basic_ostream<charT>& os, char_type a);

  Effects:
    Inserts a charT object.
  Returns:
    os << a

  static bool is_del(char_type a);

  Effects:
    Characteristic function for delimiters of charT.
  Returns:
    isspace(a)

  static int compare(const char_type* s1, const char_type* s2, size_t n);

  Effects:
        for (size_t i = 0; i < n; ++i, ++s1, ++s2)
          if (ne(*s1, *s2))
            return lt(*s1, *s2) ? -1 : 1;
        return 0;

  static size_t length(const char_type* s);

  Effects:
        size_t len = 0;
        while (ne(*s++, eos())) ++len;
        return len;

  static char_type* copy(char_type* s1, const char_type* s2, size_t n);

  Effects:
        char_type* s = s1;
        for (size_t i = 0; i < n; ++i) assign(*s1++, *s2++);
        return s;

  +-------                 BEGIN BOX 1                -------+
  Here  as elsewhere, this overconstrains implementations, in that there
  is no particular reason to do the operations in the order specified.
  +-------                  END BOX 1                 -------+

  21.1.1.3  Template class basic_string               [lib.basic.string]
  namespace std {
    template<class charT, class traits = string_char_traits<charT>,
             class Allocator = allocator>
    class basic_string {
    public:
    // types:
      typedef          traits            traits_type;
      typedef typename traits::char_type value_type;
      typedef typename Allocator::size_type       size_type;
      typedef typename Allocator::difference_type difference_type;
      typedef typename Allocator::types<charT>::reference       reference;
      typedef typename Allocator::types<charT>::const_reference const_reference;
      typedef typename Allocator::types<charT>::pointer         pointer;
      typedef typename Allocator::types<charT>::const_pointer   const_pointer;
      typedef typename Allocator::types<charT>::pointer         iterator;
      typedef typename Allocator::types<charT>::const_pointer   const_iterator;
      typedef reverse_iterator<iterator, value_type,
                      reference, difference_type>               reverse_iterator;
      typedef reverse_iterator<const_iterator, value_type,
                      const_reference, difference_type>         const_reverse_iterator;
      static const size_type npos = -1;
    // _lib.string.cons_ construct/copy/destroy:
      explicit basic_string(Allocator& = Allocator());
      basic_string(const basic_string& str, size_type pos = 0,
                   size_type n = npos, Allocator& = Allocator());
      basic_string(const charT* s, size_type n, Allocator& = Allocator());
      basic_string(const charT* s, Allocator& = Allocator());
      basic_string(size_type n, charT c, Allocator& = Allocator());
      template<class InputIterator>
        basic_string(InputIterator begin, InputIterator end,
                     Allocator& = Allocator());
     ~basic_string();
      basic_string& operator=(const basic_string& str);
      basic_string& operator=(const charT* s);
      basic_string& operator=(charT c);
    // _lib.string.iterators_ 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;

    // _lib.string.capacity_ capacity:
      size_type size() const;
      size_type length() const;
      size_type max_size() const;
      void resize(size_type n, charT c);
      void resize(size_type n);
      size_type capacity() const;
      void reserve(size_type res_arg);
      bool empty() const;
    // _lib.string.access_ element access:
      charT     operator[](size_type pos) const;
      reference operator[](size_type pos);
      const_reference at(size_type n) const;
      reference       at(size_type n);
    // _lib.string.modifiers_ modifiers:
      basic_string& operator+=(const basic_string& rhs);
      basic_string& operator+=(const charT* s);
      basic_string& operator+=(charT c);
      basic_string& append(const basic_string& str, size_type pos = 0,
                           size_type n = npos);
      basic_string& append(const charT* s, size_type n);
      basic_string& append(const charT* s);
      basic_string& append(size_type n, charT c = charT());
      template<class InputIterator>
        basic_string& append(InputIterator first, InputIterator last);
      basic_string& assign(const basic_string& str, size_type pos = 0,
                           size_type n = npos);
      basic_string& assign(const charT* s, size_type n);
      basic_string& assign(const charT* s);
      basic_string& assign(size_type n, charT c = charT());
      template<class InputIterator>
        basic_string& assign(InputIterator first, InputIterator last);
      basic_string& insert(size_type pos1, const basic_string& str,
                           size_type pos2 = 0, size_type n = npos);
      basic_string& insert(size_type pos, const charT* s, size_type n);
      basic_string& insert(size_type pos, const charT* s);
      basic_string& insert(size_type pos, size_type n, charT c = charT() );
      iterator insert(iterator p, charT c = charT());
      iterator insert(iterator p, size_type n, charT c = charT());
      template<class InputIterator>
        void insert(iterator p, InputIterator first, InputIterator last);
      basic_string& remove(size_type pos = 0, size_type n = npos);
      basic_string& remove(iterator position);
      basic_string& remove(iterator first, iterator last);
      basic_string& replace(size_type pos1, size_type n1, const basic_string& str,
                            size_type pos2 = 0, size_type n2 = npos);
      basic_string& replace(size_type pos, size_type n1, const charT* s,
                            size_type n2);
      basic_string& replace(size_type pos, size_type n1, const charT* s);
      basic_string& replace(size_type pos, size_type n, charT c = charT());

      basic_string& replace(iterator i1, iterator i2, const basic_string& str);
      basic_string& replace(iterator i1, iterator i2, const charT* s, size_type n);
      basic_string& replace(iterator i1, iterator i2, const charT* s);
      basic_string& replace(iterator i1, iterator i2,
                            size_type n, charT c = charT());
      template<class InputIterator>
        basic_string& replace(iterator i1, iterator i2,
                              InputIterator j1, InputIterator j2);
      size_type copy(charT* s, size_type n, size_type pos = 0);
      void swap(basic_string<charT,traits,Allocator>&);
    // _lib.string.ops_ string operations:
      const charT* c_str() const;  // explicit
      const charT* data() const;
      size_type find (const basic_string& str, size_type pos = 0) const;
      size_type find (const charT* s, size_type pos, size_type n) const;
      size_type find (const charT* s, size_type pos = 0) const;
      size_type find (charT c, size_type pos = 0) const;
      size_type rfind(const basic_string& str, size_type pos = npos) const;
      size_type rfind(const charT* s, size_type pos, size_type n) const;
      size_type rfind(const charT* s, size_type pos = npos) const;
      size_type rfind(charT c, size_type pos = npos) const;
      size_type find_first_of(const basic_string& str, size_type pos = 0) const;
      size_type find_first_of(const charT* s, size_type pos, size_type n) const;
      size_type find_first_of(const charT* s, size_type pos = 0) const;
      size_type find_first_of(charT c, size_type pos = 0) const;
      size_type find_last_of (const basic_string& str,
                              size_type pos = npos) const;
      size_type find_last_of (const charT* s, size_type pos, size_type n) const;
      size_type find_last_of (const charT* s, size_type pos = npos) const;
      size_type find_last_of (charT c, size_type pos = npos) const;
      size_type find_first_not_of(const basic_string& str,
                                  size_type pos = 0) const;
      size_type find_first_not_of(const charT* s, size_type pos,
                                  size_type n) const;
      size_type find_first_not_of(const charT* s, size_type pos = 0) const;
      size_type find_first_not_of(charT c, size_type pos = 0) const;
      size_type find_last_not_of (const basic_string& str,
                                  size_type pos = npos) const;
      size_type find_last_not_of (const charT* s, size_type pos,
                                  size_type n) const;
      size_type find_last_not_of (const charT* s, size_type pos = npos) const;
      size_type find_last_not_of (charT c, size_type pos = npos) const;
      basic_string substr(size_type pos = 0, size_type n = npos) const;
      int compare(const basic_string& str, size_type pos = 0,
                  size_type n = npos) const;
      int compare(charT* s, size_type pos, size_type n) const;
      int compare(charT* s, size_type pos = 0) const;
    };
  }

1 For a char-like type charT, the template class basic_string  describes
  objects  that  can  store a sequence consisting of a varying number of
  arbitrary char-like objects.  The first element of the sequence is  at

  position zero.  Such a sequence is also called a "string" if the given
  char-like type is clear from context. In  the  rest  of  this  clause,
  charT  denotes a such given char-like type.  Storage for the string is
  allocated and freed as necessary by  the  member  functions  of  class
  basic_string.

2 In all cases, size() <= capacity().

3 The functions described in this clause can report two kinds of errors,
  each associated with a distinct exception:

  --a length error is associated with exceptions  of  type  length_error
    (_lib.length.error_);

  --an   out-of-range  error  is  associated  with  exceptions  of  type
    out_of_range (_lib.out.of.range_).

  21.1.1.4  basic_string constructors                  [lib.string.cons]

1 In all basic_string constructors, a copy of the Allocator argument  is
  used  for any memory allocation performed by the constructor or member
  functions during the lifetime of the object.

  explicit basic_string(Allocator& = Allocator());

  Effects:
    Constructs an object of class basic_string.  The  postconditions  of
    this function are indicated in Table 2:

                      Table 2--basic_string() effects

                    +----------------------------------+
                    | Element            Value         |
                    +----------------------------------+
                    |data()       an unspecified value |
                    |size()       0                    |
                    |capacity()   an unspecified value |
                    +----------------------------------+

  basic_string(const basic_string<charT,traits,Allocator>& str,
               size_type pos = 0, size_type n = npos,
               Allocator& = Allocator());

  +-------                 BEGIN BOX 2                -------+
  This  is  a copy constructor with an extra argument, so that it can be
  used to copy a string while changing its allocator.  Is this the  best
  way to do this?
  +-------                  END BOX 2                 -------+

  Requires:
    pos <= size()
  Throws:
    out_of_range if pos > str.size().
  Effects:
    Constructs an object of class basic_string and determines the effec­
    tive length rlen of the initial string value as the smaller of n and
    str.size() - pos, as indicated in Table 3:

      Table 3--basic_string(basic_string,size_type,size_type) effects

             +-------------------------------------------------+
             | Element                    Value                |
             +-------------------------------------------------+
             |data()       points  at  the first element of an |
             |             allocated copy of rlen elements  of |
             |             the string controlled by str begin­ |
             |             ning at position pos                |
             |size()       rlen                                |
             |capacity()   a value at least as large as size() |
             +-------------------------------------------------+

  basic_string(const charT* s, size_type n,
               Allocator& = Allocator());

  Requires:
    s shall not be a null pointer.
  Effects:
    Constructs an object of class basic_string and determines  its  ini­
    tial  string  value  from the array of charT of length n whose first
    element is designated by s, as indicated in Table 4:

           Table 4--basic_string(const charT*,size_type) effects

             +-------------------------------------------------+
             | Element                    Value                |
             +-------------------------------------------------+
             |data()       points at the first element  of  an |
             |             allocated  copy  of the array whose |
             |             first element is pointed at by s    |
             |size()       n                                   |
             |capacity()   a value at least as large as size() |
             +-------------------------------------------------+

  basic_string(const charT* s, Allocator& = Allocator());

  Requires:
    s shall not be a null pointer.
  Effects:
    Constructs an object of class basic_string and determines  its  ini­
    tial   string   value   from   the   array   of   charT   of  length
    traits::length(s) whose first element is designated by  s, as  indi­
    cated in Table 5:

                Table 5--basic_string(const charT*) effects

             +-------------------------------------------------+
             | Element                    Value                |
             +-------------------------------------------------+
             |data()       points  at  the first element of an |
             |             allocated copy of the  array  whose |
             |             first element is pointed at by s    |
             |size()       traits::length(s)                   |
             |capacity()   a value at least as large as size() |
             +-------------------------------------------------+
  Notes:
    Uses traits::length().

  basic_string(size_type n, charT c, Allocator& = Allocator());

  Requires:
    n < npos
  Throws:
    length_error if n == npos.
  Effects:
    Constructs  an  object of class basic_string and determines its ini­
    tial string value by repeating the char-like object c for all n ele­
    ments, as indicated in Table 6:

               Table 6--basic_string(charT,size_type) effects

             +-------------------------------------------------+
             | Element                    Value                |
             +-------------------------------------------------+
             |data()       points  at  the first element of an |
             |             allocated array of n elements, each |
             |             storing the initial value c         |
             |size()       n                                   |
             |capacity()   a value at least as large as size() |
             +-------------------------------------------------+

  template<class InputIterator>
    basic_string(InputIterator begin, InputIterator end,
                 Allocator& = Allocator());

  Effects:
    Constructs  a  string  from the values in the range [begin, end), as
    indicated in Table 7:

                  Table 7--basic_string(begin,end) effects

             +-------------------------------------------------+
             | Element                    Value                |
             +-------------------------------------------------+
             |data()       points at the first element  of  an |
             |             allocated  copy  of the elements in |
             |             the range [first,last)              |
             |size()       distance between first and last     |
             |capacity()   a value at least as large as size() |
             +-------------------------------------------------+
  Notes:
    see Table ___, subclause _lib.sequence.requirements_.

  basic_string<charT,traits,Allocator>&
    operator=(const basic_string<charT,traits,Allocator>& str);

  Returns:
    *this = basic_string<charT,traits,Allocator>(str).

  basic_string<charT,traits,Allocator>&
    operator=(const charT* s);

  Returns:
    *this = basic_string<charT,traits,Allocator>(s).
  Notes:
    Uses traits::length().

  basic_string<charT,traits,Allocator>& operator=(charT c);

  Returns:
    *this = basic_string<charT,traits,Allocator>(c).

  21.1.1.5  basic_string iterator support         [lib.string.iterators]

  iterator       begin();
  const_iterator begin() const;

  Returns:
    an iterator referring to the first character in the string.

  iterator       end();
  const_iterator end() const;

  Returns:
    an iterator which is the past-the-end value.

  reverse_iterator       rbegin();
  const_reverse_iterator rbegin() const;

  Returns:
    an    iterator    which    is     semantically     equivalent     to
    reverse_iterator(end()).

  reverse_iterator       rend();
  const_reverse_iterator rend() const;

  Returns:
    an     iterator     which     is    semantically    equivalent    to
    reverse_iterator(begin()).

  21.1.1.6  basic_string capacity                  [lib.string.capacity]

  size_type size() const;

  Returns:
    a count of the number of char-like objects currently in the  string.
  Notes:
    Uses traits::length().

  size_type length() const;

  Returns:
    size().

  size_type max_size() const;

  Returns:
    The maximum size of the string.

  void resize(size_type n, charT c);

  Requires:
    n != npos

  Throws:
    length_error if n == npos.
  Effects:
    Alters the length of the string designated by *this as follows:

  --If n <= size(), the function replaces the string designated by *this
    with a string of length n whose elements are a copy of  the  initial
    elements of the original string designated by *this.

  --If  n > size(), the function replaces the string designated by *this
    with a string of length n whose first size() elements are a copy  of
    the  original  string  designated by *this, and whose remaining ele­
    ments are all initialized to c.

  void resize(size_type n);

  Returns:
    resize(n,eos()).
  Notes:
    Uses traits::eos().

  size_type capacity() const;

  Returns:
    the size of the allocated storage in the string.

  void reserve(size_type res_arg);

1 The  member  function  reserve()  is  a  directive  that   informs   a
  basic_string  of  a  planned change in size, so that it can manage the
  storage allocation accordingly.
  Effects:
    After reserve(), capacity() is greater or equal to the  argument  of
    reserve  if reallocation happens; and equal to the previous value of
    capacity() otherwise.
    Reallocation happens at this point if and only if the current capac­
    ity is less than the argument of reserve().
  Complexity:
    It does not change the size of the sequence and takes at most linear
    time in the size of the sequence.
  Notes:
    Reallocation invalidates all the references, pointers, and iterators
    referring to the elements in the sequence.  It is guaranteed that no
    reallocation takes place during the  insertions  that  happen  after
    reserve()  takes  place  till  the  time when the size of the string
    reaches the size specified by reserve().

  bool empty() const;

  Returns:
    size() == 0.

  21.1.1.7  basic_string element access              [lib.string.access]

  charT     operator[](size_type pos) const;
  reference operator[](size_type pos);

  Returns:
    If pos < size(), returns data()[pos].  Otherwise, if pos ==  size(),
    the const version returns traits::eos().  Otherwise, the behavior is
    undefined.
  Notes:
    The reference returned by the non-const version is invalid after any
    subsequent call to c_str(), data(), or any non-const member function
    for the object.

  const_reference at(size_type n) const;
  reference       at(size_type n);

  Requires:
    pos < size()
  Throws:
    out_of_range if pos >= size().
  Returns:
    operator[](pos).

  21.1.1.8  basic_string modifiers                [lib.string.modifiers]

  21.1.1.8.1  basic_string::operator+=                [lib.string::op+=]

  basic_string<charT,traits,Allocator>&
    operator+=(const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    append(rhs).

  basic_string<charT,traits,Allocator>& operator+=(const charT* s);

  Returns:
    *this += basic_string<charT,traits,Allocator>(s).
  Notes:
    Uses traits::length().

  basic_string<charT,traits,Allocator>& operator+=(charT c);

  Returns:
    *this += basic_string<charT,traits,Allocator>(c).

  21.1.1.8.2  basic_string::append                  [lib.string::append]

  basic_string<charT,traits,Allocator>&
    append(const basic_string<charT,traits>& str, size_type pos = 0,
           size_type n = npos);

  Requires:
    pos <= size()
  Throws:
    out_of_range if pos > str.size().
  Effects:
    Determines the effective length rlen of the string to append as  the
    smaller  of  n  and  str.size()  -  pos.   The  function then throws
    length_error if size() >= npos - rlen.
    Otherwise, the function replaces the string controlled by *this with
    a  string  of length size() + rlen whose first size() elements are a
    copy of the original string controlled by *this and whose  remaining
    elements are a copy of the initial elements of the string controlled
    by str beginning at position pos.
  Returns:
    *this.

  basic_string<charT,traits,Allocator>&
    append(const charT* s, size_type n);

  Returns:
    append(basic_string<charT,traits,Allocator>(s,n)).

  basic_string<charT,traits,Allocator>& append(const charT* s);

  Returns:
    append(basic_string<charT,traits,Allocator>(s)).
  Notes:
    Uses traits::length().

  basic_string<charT,traits,Allocator>&
    append(size_type n, charT c = charT());

  Returns:
    append(basic_string<charT,traits,Allocator>(c,n)).

  template<class InputIterator>
    basic_string& append(InputIterator first, InputIterator last);

  Returns:
    append(basic_string<charT,traits,Allocator>(first,last)).

  21.1.1.8.3  basic_string::assign                  [lib.string::assign]

  basic_string<charT,traits,Allocator>&
    assign(const basic_string<charT,traits>& str, size_type pos = 0,
           size_type n = npos);

  Requires:
    pos <= size()
  Throws:
    out_of_range if pos > str.size().
  Effects:
    Determines the effective length rlen of the string to assign as  the
    smaller of n and str.size() - pos.
    The  function  then  replaces  the string controlled by *this with a
    string of length rlen whose elements are a copy of the  string  con­
    trolled by str beginning at position pos.
  Returns:
    *this.

  basic_string<charT,traits,Allocator>&
    assign(const charT* s, size_type n);

  Returns:
    assign(basic_string<charT,traits,Allocator>(s,n)).

  basic_string<charT,traits,Allocator>& assign(const charT* s);

  Returns:
    assign(basic_string(s)).
  Notes:
    Uses traits::length().

  basic_string<charT,traits,Allocator>&
    assign(size_type n, charT c = charT());

  Returns:
    assign(basic_string<charT,traits,Allocator>(c,n)).

  template<class InputIterator>
    basic_string& assign(InputIterator first, InputIterator last);

  Returns:
    assign(basic_string<charT,traits,Allocator>(first,last)).

  21.1.1.8.4  basic_string::insert                  [lib.string::insert]

  basic_string<charT,traits,Allocator>&
    insert(size_type pos1,
           const basic_string<charT,traits,Allocator>& str,
           size_type pos2 = 0, size_type n = npos);

  Requires
    pos1 <= size()
  Throws:
    out_of_range if pos1 > size() or pos2 > str.size().
  Effects:
    Determines  the effective length rlen of the string to insert as the
    smaller of n and str.size() - pos2.   Then  throws  length_error  if
    size() >= npos - rlen.
    Otherwise, the function replaces the string controlled by *this with
    a string of length size() + rlen whose first  pos1  elements  are  a
    copy  of  the  initial elements of the original string controlled by
    *this, whose next rlen elements are a copy of the  elements  of  the
    string  controlled  by  str  beginning  at  position pos2, and whose
    remaining elements are a copy of the remaining elements of the orig­
    inal string controlled by *this.
  Returns:
    *this.

  basic_string<charT,traits,Allocator>&
    insert(size_type pos, const charT* s, size_type n);

  Returns:
    insert(pos,basic_string<charT,traits,Allocator>(s,n)).

  basic_string<charT,traits,Allocator>&
    insert(size_type pos, const charT* s);

  Returns:
    insert(pos,basic_string<charT,traits,Allocator>(s)).
  Notes:
    Uses traits::length().

  basic_string<charT,traits,Allocator>&
    insert(size_type pos, size_type n, charT c = charT());

  Returns:
    insert(pos,basic_string<charT,traits,Allocator>(c,n)).

  iterator insert(iterator p, charT c = charT());

  Requires:
    p is a valid iterator on *this.
  Effects:
    inserts a copy of c before the character referred to by p.
  Returns:
    p.

  iterator insert(iterator p, size_type n, charT c = charT());

  Requires:
    p is a valid iterator on *this.
  Effects:
    inserts n copies of c before the character referrred to by p.

  template<class InputIterator>
    void insert(iterator p, InputIterator first, InputIterator last);

  Requires:
    p is a valid iterator on *this.  [first,last) is a valid range.
  Effects:
    inserts  copies  of  the characters in the range [first,last) before
    the character referrred to by p.

  21.1.1.8.5  basic_string::remove                  [lib.string::remove]

  basic_string<charT,traits,Allocator>&
    remove(size_type pos = 0, size_type n = npos);

  Requires:
    pos  <= size()
  Throws:
    out_of_range if pos  > size().
  Effects:
    Determines the effective length xlen of the string to be removed  as
    the smaller of n and size() - pos.
    The  function  then  replaces  the string controlled by *this with a
    string of length size() - xlen whose first pos elements are  a  copy
    of  the initial elements of the original string controlled by *this,
    and whose remaining elements are a copy of the elements of the orig­
    inal string controlled by *this beginning at position pos + xlen.
  Returns:
    *this.

  basic_string& remove(iterator p);

  Requires:
    p is a valid iterator on *this.
  Effects:
    removes  the  character  referred  to by p and calls the character's

    destructor.
  Returns:
    *this.

  basic_string& remove(iterator first, iterator last);

  Requires:
    first and last are  valid  iterators  on  *this,  defining  a  range
    [first,last).
  Effects:
    removes the characters in the range [first,last) and calls the char­
    acter's destructor.
  Complexity:
    the destructor is called a number of times exactly equal to the size
    of the range.
  Returns:
    *this.

  21.1.1.8.6  basic_string::replace                [lib.string::replace]

  basic_string<charT,traits,Allocator>&
    replace(size_type pos1, size_type n1,
            const basic_string<charT,traits,Allocator>& str,
            size_type pos2 = 0, size_type n2 = npos);

  Requires:
    pos1 <= size() && pos2 <= size().
  Throws:
    out_of_range if pos1 > size() or pos2 > str.size().
  Effects:
    Determines  the effective length xlen of the string to be removed as
    the smaller of n1 and size() - &pos1.  It also determines the effec­
    tive  length  rlen of the string to be inserted as the smaller of n2
    and str.size() - pos2 .
    Throws length_error if size() - xlen >= npos - rlen.
    Otherwise, the function replaces the string controlled by *this with
    a  string  of  length size() - xlen + rlen whose first pos1 elements
    are a copy of the initial elements of the original string controlled
    by  *this,  whose  next rlen elements are a copy of the initial ele­
    ments of the string controlled by str beginning  at  position  pos2,
    and whose remaining elements are a copy of the elements of the orig­
    inal string controlled by *this beginning at position pos1 + xlen.
  Returns:
    *this.

  basic_string<charT,traits,Allocator>&
    replace(size_type pos, size_type n1, const charT* s, size_type n2);

  Returns:
    replace(pos,n1,basic_string<charT,traits,Allocator>(s,n2)).

  basic_string<charT,traits,Allocator>&
    replace(size_type pos, size_type n1, const charT* s);

  Returns:
    replace(pos,n1,basic_string<charT,traits,Allocator>(s)).
  Notes:
    Uses traits::length().

  basic_string<charT,traits,Allocator>&
    replace(size_type pos, size_type n, charT c = charT());

  Returns:
    replace(pos,n,basic_string<charT,traits,Allocator>(c,n)).

  basic_string& replace(iterator i1, iterator i2, const basic_string& str);

  Requires:
    The iterators i1 and i2 are valid iterators  on  *this,  defining  a
    range [i1,i2).
  Effects:
    Replaces  the  string  controlled  by  *this with a string of length
    size() - (i2 - i1) + str.size() whose first begin()  -  i1  elements
    are a copy of the initial elements of the original string controlled
    by *this, whose next str.size() elements are a copy  of  the  string
    controlled  by  str,  and whose remaining elements are a copy of the
    elements of the original string controlled  by  *this  beginning  at
    position i2.
  Returns:
    *this.
  Notes:
    After  the  call,  the  length  of  the  string  will be changed by:
    str.size() - (i2 - i1).

  basic_string&
    replace(iterator i1, iterator i2, const charT* s, size_type n);

  Returns:
    replace(i1,i2,basic_string(s,n)).
  Notes:
    Length change: n - (i2 - i1).

  basic_string& replace(iterator i1, iterator i2, const charT* s);

  Returns:
    replace(i1,i2,basic_string(s)).
  Notes:
    Length change: traits::length(s) - (i2 - i1).
    Uses traits::length().

  basic_string& replace(iterator i1, iterator i2, size_type n,
                        charT c = charT());

  Returns:
    replace(i1,i2,basic_string(n,c)).
  Notes:
    Length change: n - (i2 - i1).

  template<class InputIterator>
    basic_string& replace(iterator i1, iterator i2,
                          InputIterator j1, InputIterator j2);

  Returns:
    replace(i1,i2,basic_string(j1,j2)).
  Notes:
    Length change: j2 - j1 - (i2 - i1).

  21.1.1.8.7  basic_string::copy                      [lib.string::copy]

  size_type copy(charT* s, size_type n, size_type pos = 0);

  Requires:
    pos <= size()
  Throws:
    out_of_range if pos > size().
  Effects:
    Determines the effective length rlen of the string to  copy  as  the
    smaller  of  n  and  size() - pos.  s shall designate an array of at
    least rlen elements.
    The function then replaces the string designated by s with a  string
    of length rlen whose elements are a copy of the string controlled by
    *this beginning at position pos.
  Notes:
    The function does not append a null object to the string.
  Returns:
    rlen.

  21.1.1.8.8  basic_string::swap                      [lib.string::swap]

  void swap(basic_string<charT,traits,Allocator>& s);

  Effects:
    Swaps the contents of the two strings.
  Postcondition:
    *this contains the characters that were in s, s contains the charac­
    ters that were in *this.
  Complexity:
    Constant time.

  21.1.1.9  basic_string string operations              [lib.string.ops]

  const charT* c_str() const;

  Returns:
    A  pointer  to  the initial element of an array of length size() + 1
    whose first size() elements equal the corresponding elements of  the
    string  controlled by *this and whose last element is a null charac­
    ter specified by traits::eos().
  Requires:
    The program shall not alter any of the values stored in  the  array.
    Nor  shall  the  program treat the returned value as a valid pointer
    value after any subsequent call to a non-const  member  function  of
    the class basic_string that designates the same object as this.
  Notes:
    Uses traits::eos().

  const charT* data() const;

  Returns:
    c_str() if size() is nonzero, otherwise a null pointer.
  Requires:
    The  program shall not alter any of the values stored in the charac­
    ter array.  Nor shall the program treat  the  returned  value  as  a
    valid pointer value after any subsequent call to a non- const member
    function of basic_string that designates the same object as this.

  21.1.1.9.1  basic_string::find                      [lib.string::find]

  size_type find(const basic_string<charT,traits,Allocator>& str,
                 size_type pos = 0) const;

  Effects:
    Determines the lowest position xpos, if possible, such that both  of
    the following conditions obtain:

  --pos <= xpos and xpos + str.size() <= size();

  --at(xpos+I)  == str.at(I) for all elements I of the string controlled
    by str.
  Returns:
    xpos if the function can determine such a value  for  xpos.   Other­
    wise, returns npos.
  Notes:
    Uses traits::eq().

  size_type find(const charT* s, size_type pos, size_type n) const;

  Returns:
    find(basic_string<charT,traits,Allocator>(s,n)pos).

  size_type find(const charT* s, size_type pos = 0) const;

  Returns:
    find(basic_string<charT,traits,Allocator>(s),pos).
  Notes:
    Uses traits::length().

  size_type find(charT c, size_type pos = 0) const;

  Returns:
    find(basic_string<charT,traits,Allocator>(c),pos).

  21.1.1.9.2  basic_string::rfind                    [lib.string::rfind]

  size_type rfind(const basic_string<charT,traits,Allocator>& str,
                  size_type pos = npos) const;

  Effects:
    Determines the highest position xpos, if possible, such that both of
    the following conditions obtain:

  --xpos <= pos and xpos + str.size() <= size();

  --at(xpos+I) == str.at(I) for all elements I of the string  controlled
    by str.
  Returns:
    xpos  if  the  function can determine such a value for xpos.  Other­
    wise, returns npos.
  Notes:
    Uses traits::eq().

  size_type rfind(const charT* s, size_type pos, size_type n) const;

  Returns:
    rfind(basic_string<charT,traits,Allocator>(s,n),pos).

  size_type rfind(const charT* s, size_type pos = npos) const;

  Returns:
    rfind(basic_string<charT,traits,Allocator>(s),pos).
  Notes:
    Uses traits::length().

  size_type rfind(charT c, size_type pos = npos) const;

  Returns:
    rfind(basic_string<charT,traits,Allocator>(c,n),pos).

  21.1.1.9.3                                 [lib.string::find.first.of]
       basic_string::find_first_of

  size_type
    find_first_of(const basic_string<charT,traits,Allocator>& str,
                  size_type pos = 0) const;

  Effects:
    Determines  the lowest position xpos, if possible, such that both of
    the following conditions obtain:

  --pos <= xpos and xpos < size();

  --at(xpos) == str.at(I) for some element I of the string controlled by
    str.
  Returns:
    xpos  if  the  function can determine such a value for xpos.  Other­
    wise, returns npos.
  Notes:
    Uses traits::eq().

  size_type
    find_first_of(const charT* s, size_type pos, size_type n) const;

  Returns:
    find_first_of(basic_string<charT,traits,Allocator>(s,n),pos).

  size_type find_first_of(const charT* s, size_type pos = 0) const;

  Returns:
    find_first_of(basic_string<charT,traits,Allocator>(s),pos).
  Notes:
    Uses traits::length().

  size_type find_first_of(charT c, size_type pos = 0) const;

  Returns:
    find_first_of(basic_string<charT,traits,Allocator>(c),pos).

  21.1.1.9.4  basic_string::find_last_of      [lib.string::find.last.of]

  size_type
    find_last_of(const basic_string<charT,traits,Allocator>& str,
                 size_type pos = npos) const;

  Effects:
    Determines the highest position xpos, if possible, such that both of
    the following conditions obtain:

  --xpos <= pos and pos < size();

  --at(xpos) == str.at(I) for some element I of the string controlled by
    str.
  Returns:
    xpos  if  the  function can determine such a value for xpos.  Other­
    wise, returns npos.
  Notes:
    Uses traits::eq().

  size_type find_last_of(const charT* s, size_type pos, size_type n) const;

  Returns:
    find_last_of(basic_string<charT,traits,Allocator>(s,n),pos).

  size_type find_last_of(const charT* s, size_type pos = npos) const;

  Returns:
    find_last_of(basic_string<charT,traits,Allocator>(s),pos).
  Notes:
    Uses traits::length().

  size_type find_last_of(charT c, size_type pos = npos) const;

  Returns:
    find_last_of(basic_string<charT,traits,Allocator>(c),pos).

  21.1.1.9.5                             [lib.string::find.first.not.of]
       basic_string::find_first_not_of

  size_type
    find_first_not_of(const basic_string<charT,traits,Allocator>& str,
                      size_type pos = 0) const;

  Effects:
    Determines the lowest position xpos, if possible, such that both  of
    the following conditions obtain:

  --pos <= xpos and xpos < size();

  --at(xpos)  ==  str.at(I) for no element I of the string controlled by
    str.
  Returns:
    xpos if the function can determine such a value  for  xpos.   Other­
    wise, returns npos.

  Notes:
    Uses traits::eq().

  size_type
    find_first_not_of(const charT* s, size_type pos, size_type n) const;

  Returns:
    find_first_not_of(basic_string<charT,traits,Allocator>(s,n),pos).

  size_type find_first_not_of(const charT* s, size_type pos = 0) const;

  Returns:
    find_first_not_of(basic_string<charT,traits,Allocator>(s),pos).
  Notes:
    Uses traits::length().

  size_type find_first_not_of(charT c, size_type pos = 0) const;

  Returns:
    find_first_not_of(basic_string<charT,traits,Allocator>(c),pos).

  21.1.1.9.6                              [lib.string::find.last.not.of]
       basic_string::find_last_not_of

  size_type
    find_last_not_of(const basic_string<charT,traits,Allocator>& str,
                     size_type pos = npos) const;

  Effects:
    Determines the highest position xpos, if possible, such that both of
    the following conditions obtain:

  --xpos <= pos and pos < size();

  --at(xpos) == str.at(I)) for no element I of the string controlled  by
    str.
  Returns:
    xpos  if  the  function can determine such a value for xpos.  Other­
    wise, returns npos.
  Notes:
    Uses traits::eq().

  size_type find_last_not_of(const charT* s, size_type pos,
                             size_type n) const;

  Returns:
    find_last_not_of(basic_string<charT,traits,Allocator>(s,n),pos).

  size_type find_last_not_of(const charT* s, size_type pos = npos) const;

  Returns:
    find_last_not_of(basic_string<charT,traits,Allocator>(s),pos).
  Notes:
    Uses traits::length().

  size_type find_last_not_of(charT c, size_type pos = npos) const;

  Returns:
    find_last_not_of(basic_string<charT,traits,Allocator>(c),pos).

  21.1.1.9.7  basic_string::substr                  [lib.string::substr]

  basic_string<charT,traits,Allocator>
    substr(size_type pos = 0, size_type n = npos) const;

  Requires:
    pos <= size()
  Throws:
    out_of_range if pos > size().
  Effects:
    Determines the effective length rlen of the string to  copy  as  the
    smaller of n and size() - pos.
  Returns:
    basic_string<charT,traits,Allocator>(data()+pos,rlen).

  21.1.1.9.8  basic_string::compare                [lib.string::compare]

  int compare(const basic_string<charT,traits,Allocator>& str,
              size_type pos = 0, size_type n = npos)

  Requires:
    pos <= size()
  Throws:
    out_of_range if pos > size().
  Effects:
    Determines  the  effective  length rlen of the strings to compare as
    the smallest of n, size() - pos , and str.size().  The function then
    compares        the        two        strings       by       calling
    traits::compare(data()+pos,str.data(),rlen).
  Returns:
    the nonzero result if the result of the comparison is nonzero.  Oth­
    erwise, returns a value as indicated in Table 8:

                         Table 8--compare() results

                 +----------------------------------------+
                 |       Condition           Return Value |
                 +----------------------------------------+
                 |size()-pos <  str.size()   < 0          |
                 |size()-pos == str.size()     0          |
                 |size()-pos >  str.size()   > 0          |
                 +----------------------------------------+
  Notes:
    Uses traits::compare().

  int compare(const charT* s, size_type pos, size_type n) const;

  Returns:
    compare(basic_string<charT,traits,Allocator>(s,n),pos).
  Notes:
    Uses traits::compare().

  int compare(const charT* s, size_type pos = 0) const;

  Returns:
    compare(basic_string<charT,traits,Allocator>(s),pos).
  Notes:
    Uses traits::length() and traits::compare().

  21.1.1.10  basic_string non-member             [lib.string.nonmembers]
       functions

  21.1.1.10.1  operator+                               [lib.string::op+]

  template<class charT, class traits, class Allocator>
    basic_string<charT,traits,Allocator>
      operator+(const basic_string<charT,traits,Allocator>& lhs,
                const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    lhs.append(rhs).

  template<class charT, class traits, class Allocator>
    basic_string<charT,traits,Allocator>
      operator+(const charT* lhs,
                const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    basic_string<charT,traits,Allocator>(lhs) + rhs.

  Notes:
    Uses traits::length().

  template<class charT, class traits, class Allocator>
    basic_string<charT,traits,Allocator>
      operator+(charT lhs,
                const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    basic_string<charT,traits,Allocator>(lhs) + rhs.

  template<class charT, class traits, class Allocator>
    basic_string<charT,traits,Allocator>
      operator+(const basic_string<charT,traits,Allocator>& lhs,
                const charT* rhs);

  Returns:
    lhs + basic_string<charT,traits,Allocator>(rhs).
  Notes:
    Uses traits::length().

  template<class charT, class traits, class Allocator>
    basic_string<charT,traits,Allocator>
      operator+(const basic_string<charT,traits,Allocator>& lhs,
                charT rhs);

  Returns:
    lhs + basic_string<charT,traits,Allocator>(rhs).

  21.1.1.10.2  operator==                       [lib.string::operator==]

  template<class charT, class traits, class Allocator>
    bool operator==(const basic_string<charT,traits,Allocator>& lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    lhs.compare(rhs) == 0.

  template<class charT, class traits, class Allocator>
    bool operator==(const charT* lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    basic_string<charT,traits,Allocator>(lhs) == rhs.

  template<class charT, class traits, class Allocator>
    bool operator==(const basic_string<charT,traits,Allocator>& lhs,
                    const charT* rhs);

  Returns:
    lhs == basic_string<charT,traits,Allocator>(rhs).
  Notes:
    Uses traits::length().

  21.1.1.10.3  operator!=                             [lib.string::op!=]

  template<class charT, class traits, class Allocator>
    bool operator!=(const basic_string<charT,traits,Allocator>& lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    !(lhs == rhs).

  template<class charT, class traits, class Allocator>
    bool operator!=(const charT* lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    basic_string<charT,traits,Allocator>(lhs) != rhs.

  template<class charT, class traits, class Allocator>
    bool operator!=(const basic_string<charT,traits,Allocator>& lhs,
                    const charT* rhs);

  Returns:
    lhs != basic_string<charT,traits,Allocator>(rhs).
  Notes:
    Uses traits::length().

  21.1.1.10.4  operator<                               [lib.string::op<]

  template<class charT, class traits, class Allocator>
    bool operator< (const basic_string<charT,traits,Allocator>& lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    lhs.compare(rhs) < 0.

  template<class charT, class traits, class Allocator>
    bool operator< (const charT* lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    basic_string<charT,traits,Allocator>(lhs) < rhs.

  template<class charT, class traits, class Allocator>
    bool operator< (const basic_string<charT,traits,Allocator>& lhs,
                    const charT* rhs);

  Returns:
    lhs < basic_string<charT,traits,Allocator>(rhs).

  21.1.1.10.5  operator>                               [lib.string::op>]

  template<class charT, class traits, class Allocator>
    bool operator> (const basic_string<charT,traits,Allocator>& lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    lhs.compare(rhs) > 0.

  template<class charT, class traits, class Allocator>
    bool operator> (const charT* lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    basic_string<charT,traits,Allocator>(lhs) > rhs.

  template<class charT, class traits, class Allocator>
    bool operator> (const basic_string<charT,traits,Allocator>& lhs,
                    const charT* rhs);

  Returns:
    lhs > basic_string<charT,traits,Allocator>(rhs).

  21.1.1.10.6  operator<=                             [lib.string::op<=]

  template<class charT, class traits, class Allocator>
    bool operator<=(const basic_string<charT,traits,Allocator>& lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    lhs.compare(rhs) <= 0.

  template<class charT, class traits, class Allocator>
    bool operator<=(const charT* lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    basic_string<charT,traits,Allocator>(lhs) <= rhs.

  template<class charT, class traits, class Allocator>
    bool operator<=(const basic_string<charT,traits,Allocator>& lhs,
                    const charT* rhs);

  Returns:
    lhs <= basic_string<charT,traits,Allocator>(rhs).

  21.1.1.10.7  operator>=                             [lib.string::op>=]

  template<class charT, class traits, class Allocator>
    bool operator>=(const basic_string<charT,traits,Allocator>& lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    lhs.compare(rhs) >= 0.

  template<class charT, class traits, class Allocator>
    bool operator>=(const charT* lhs,
                    const basic_string<charT,traits,Allocator>& rhs);

  Returns:
    basic_string<charT,traits,Allocator>(lhs) >= rhs.

  template<class charT, class traits, class Allocator>
    bool operator>=(const basic_string<charT,traits,Allocator>& lhs,
                    const charT* rhs);

  Returns:
    lhs <= basic_string<charT,traits,Allocator>(rhs).

  21.1.1.10.8  Inserters and extractors

  template<class charT, class traits, class Allocator>
    basic_istream<charT>&
      operator>>(basic_istream<charT>& is,
                 basic_string<charT,traits,Allocator>& str);

  Notes:
    Uses traits::char_in and is_del().

  template<class charT, class traits, class Allocator>
    basic_ostream<charT>&
      operator<<(basic_ostream<charT>& os,
                 const basic_string<charT,traits,Allocator>& str);

  Notes:
    Uses traits::char_out().

  template<class charT, class IS_traits, class STR_traits,
           class STR_Alloc>
    basic_istream<charT,IS_traits>&
      getline(basic_istream<charT,IS_traits>& is,
              basic_string<charT,STR_traits,STR_Alloc>& str,
              charT delim = IS_traits::newline() );

  Effects:
    An unformatted input function, extracts  a  line  (as  delimited  by
    delim) from is into str.
    The  string  is initially made empty by calling str.remove(0).  Each
    extracted character c is appended as if  by  calling  str.append(c).
    Characters  are  extracted  and  appended until any of the following
    occurs:

  --npos - 1 characters are appended (in which case the  function  calls
    is.setstate(failbit),     which    may    throw    ios_base::failure
    (_lib.iostate.flags_)).

  --end of file occurs on the input sequence (in which case the function
    calls   is.setstate(eofbit),   which   may  throw  ios_base::failure
    (_lib.iostate.flags_)).

  --c == delim for the next available input character c (in  which  case
    the  input character is extracted from is, but not appended to str).
    If    the    function    appends    no    characters,    it    calls
    is.setstate(failbit),     which    may    throw    ios_base::failure
    (_lib.iostate.flags_).
  Returns:
    is.
  Notes:
    Uses STR_traits::char_in().

  21.1.2  Class string                                      [lib.string]
  namespace std {
    struct string_char_traits<char> {
      typedef char char_type;
      static void assign(char& c1, const char& c2);
      static bool eq(const char& c1, const char& c2);
      static bool ne(const char& c1, const char& c2);
      static bool lt(const char& c1, const char& c2);
      static char eos();
      static basic_istream<char>& char_in (basic_istream<char>& is, char& a);
      static basic_ostream<char>& char_out(basic_ostream<char>& os, char a);
      static bool is_del(char a); // characteristic function for delimiters
      static int compare(const char* s1, const char* s2, size_t n);
      static size_type length(const char* s);
      static char* copy(char* s1, const char* s2, size_t n);
    };
    typedef basic_string<char> string;
  }

  21.1.3  string_char_traits<char>           [lib.string.traits.members]
       members

  static void assign(char& c1, const char& c2);

  Effects:
    c1 = c2.

  static bool eq(const char& c1, const char& c2);

  Returns:
    c1 == c2.

  static bool ne(const char& c1, const char& c2);

  Returns:
    c1 != c2.

  static bool lt(const char& c1, const char& c2);

  Returns:
    c1 < c2.

  static char eos();

  Returns:
    0.

  basic_istream<char>& char_in (basic_istream<char>& is, char& a);

  Returns:
    is >> a .

  basic_ostream<char>& char_out(basic_ostream<char>& os, char a);

  Returns:
    os << a.

  bool is_del(char a);

  Returns:
    ::isspace(a).

  static int compare(const char* s1, const char* s2, size_t n);

  Returns:
    ::memcmp(s1,s2,n).

  static size_type length(const char* s);

  Returns:
    ::strlen(s).

  static char* copy(char* s1, const char* s2, size_t n);

  Returns:
    ::memcpy(s1,s2,n).

  21.1.4  Class wstring                                    [lib.wstring]
  namespace std {
    struct string_char_traits<wchar_t> {
      typedef wchar_t char_type;
      static void assign(wchar_t& c1, const wchar_t& c2);
      static bool eq(const wchar_t& c1, const wchar_t& c2);
      static bool ne(const wchar_t& c1, const wchar_t& c2);
      static bool lt(const wchar_t& c1, const wchar_t& c2);
      static wchar_t eos();
      static basic_istream<wchar_t>& char_in (basic_istream<wchar_t>& is, wchar_t& a);
      static basic_ostream<wchar_t>& char_out(basic_ostream<wchar_t>& os, wchar_t a);
      static bool is_del(wchar_t a); // characteristic function for delimiters
      static int compare(const wchar_t* s1, const wchar_t* s2, size_t n);
      static size_type length(const wchar_t* s);
      static wchar_t* copy(wchar_t* s1, const wchar_t* s2, size_t n);
    };
    typedef basic_string<wchar_t> wstring;
  }

  21.1.5  string_char_traits<wchar_t> members      [lib.wstring.members]

  static void assign(wchar_t& c1, const wchar_t& c2);

  Effects:
    c1 = c2.

  static bool eq(const wchar_t& c1, const wchar_t& c2);

  Returns:
    c1 == c2.

  static bool ne(const wchar_t& c1, const wchar_t& c2);

  Returns:
    c1 != c2.

  static bool lt(const wchar_t& c1, const wchar_t& c2);

  Returns:
    c1 < c2.

  static wchar_t eos();

  Returns:
    0.

  basic_istream<wchar_t>& char_in (basic_istream<wchar_t>& is, wchar_t& a);

  Returns:
    is >> a .

  basic_ostream<wchar_t>& char_out(basic_ostream<wchar_t>& os, wchar_t a);

  Returns:
    os << a.

  bool is_del(wchar_t a);

  Returns:
    ::iswspace(a).

  static int compare(const wchar_t* s1, const wchar_t* s2, size_t n);

  Returns:
    ::wmemcmp(s1,s2,n).

  static size_type length(const wchar_t* s);

  Returns:
    ::wcslen(s).

  static wchar_t* copy(wchar_t* s1, const wchar_t* s2, size_t n);

  Returns:
    ::wmemcpy(s1,s2,n).

  21.2  Null-terminated sequence utilities               [lib.c.strings]

1 Headers <cctype>, <cwctype>, <cstring>, <cwchar>, <cstdlib> (multibyte
  conversions), and <ciso646>.

                    Table 8--Header <cctype> synopsis

            +-------------------------------------------------+
            | Type                    Name(s)                 |
            +-------------------------------------------------+
            |Functions:                                       |
            |isalnum   isdigit   isprint   isupper    tolower |
            |isalpha   isgraph   ispunct   isxdigit   toupper |
            |iscntrl   islower   isspace                      |
            +-------------------------------------------------+

                    Table 8--Header <cwctype> synopsis

   +------------------------------------------------------------------+
   |  Type                            Name(s)                         |
   +------------------------------------------------------------------+
   |Macro:     WEOF <cwctype>                                         |
   +------------------------------------------------------------------+
   |Types:     wctrans_t   wctype_t   wint_t <cwctype>                |
   +------------------------------------------------------------------+
   |Functions:                                                        |
   |iswalnum   iswctype    iswlower   iswspace    towctrans   wctrans |
   |iswalpha   iswdigit    iswprint   iswupper    towlower    wctype  |
   |iswcntrl   iswgraph    iswpunct   iswxdigit   towupper            |
   +------------------------------------------------------------------+

                    Table 8--Header <cstring> synopsis

            +-------------------------------------------------+
            | Type                    Name(s)                 |
            +-------------------------------------------------+
            |Macro:    NULL <cstring>                         |
            +-------------------------------------------------+
            |Type:     size_type <cstring>                    |
            +-------------------------------------------------+
            |Functions:                                       |
            |strcoll              strlen    strpbrk   strtok  |
            |strcat    strcpy     strncat   strrchr   strxfrm |
            |strchr    strcspn    strncmp   strspn            |
            |strcmp    strerror   strncpy   strstr            |
            +-------------------------------------------------+

                    Table 8--Header <cwchar> synopsis

  +------------------------------------------------------------------------+
  |  Type                               Name(s)                            |
  +------------------------------------------------------------------------+
  |Macros:    NULL <cwchar>   WCHAR_MAX   WCHAR_MIN   WEOF <cwchar>        |
  +------------------------------------------------------------------------+
  |Types:     mbstate_t       wint_t <cwchar>                              |
  +------------------------------------------------------------------------+
  |Functions:                                                              |
  |btowc      getwchar        ungetwc     wcscpy      wcsrtombs   wmemchr  |
  |fgetwc     mbrlen          vfwprintf   wcscspn     wcsspn      wmemcmp  |
  |fgetws     mbrtowc         vswprintf   wcsftime    wcsstr      wmemcpy  |
  |fputwc     mbsinit         vwprintf    wcslen      wcstod      wmemmove |
  |fputws     mbsrtowcs       wcrtomb     wcsncat     wcstok      wmemset  |
  |fwide      putwc           wcscat      wcsncmp     wcstol      wprintf  |
  |fwprintf   putwchar        wcschr      wcsncpy     wcstoul     wscanf   |
  |fwscanf    swprintf        wcscmp      wcspbrk     wcsxfrm              |
  |getwc      swscanf         wcscoll     wcsrchr     wctob                |
  +------------------------------------------------------------------------+

                    Table 8--Header <cstdlib> synopsis

                +-----------------------------------------+
                | Type                Name(s)             |
                +-----------------------------------------+
                |Macros:   MB_CUR_MAX                     |
                +-----------------------------------------+
                |Functions:                               |
                |atol      mblen        strtod   wctomb   |
                |atof      mbstowcs     strtol   wcstombs |
                |atoi      mbtowc       stroul            |
                +-----------------------------------------+

2 The  contents are the same as the Standard C library, with the follow­
  ing modifications:

3 None of the headers shall define the type wchar_t (_lex.key_).

4 The function signature strchr(const char*, int) is replaced by the two
  declarations:

  const char* strchr(const char* s, int c);
        char* strchr(      char* s, int c);

5 both of which have the same behavior as the original declaration.

6 The  function  signature strpbrk(const char*, const char*) is replaced
  by the two declarations:

  const char* strpbrk(const char* s1, const char* s2);
        char* strpbrk(      char* s1, const char* s2);

7 both of which have the same behavior as the original declaration.

8 The function signature strrchr(const char*, int) is  replaced  by  the
  two declarations:

  const char* strrchr(const char* s, int c);
        char* strrchr(      char* s, int c);

9 both of which have the same behavior as the original declaration.

10The function signature strstr(const char*, const char*) is replaced by
  the two declarations:

  const char* strstr(const char* s1, const char* s2);
        char* strstr(      char* s1, const char* s2);

11both of which have the same behavior as the original declaration.

12The function signature memchr(const void*, int, size_t) is replaced by
  the two declarations:

  const void* memchr(const void* s, int c, size_t n);
        void* memchr(      void* s, int c, size_t n);

13both of which have the same behavior as the original declaration.

14The  function signature wcschr(const wchar_t*, wchar_t) is replaced by
  the two declarations:

  const wchar_t* wcschr(const wchar_t* s, wchar_t c);
        wchar_t* wcschr(      wchar_t* s, wchar_t c);

15both of which have the same behavior as the original declaration.

16The  function  signature  wcspbrk(const wchar_t*,  const wchar_t*)  is
  replaced by the two declarations:

  const wchar_t* wcspbrk(const wchar_t* s1, const wchar_t* s2);
        wchar_t* wcspbrk(      wchar_t* s1, const wchar_t* s2);

17both of which have the same behavior as the original declaration.

18The function signature wcsrchr(const wchar_t*, wchar_t) is replaced by
  the two declarations:

  const wchar_t* wcsrchr(const wchar_t* s, wchar_t c);
        wchar_t* wcsrchr(      wchar_t* s, wchar_t c);

19both of which have the same behavior as the original declaration.

20The  function  signature  wcswcs(const wchar_t*,  const wchar_t*)   is
  replaced by the two declarations:

  const wchar_t* wcsstr(const wchar_t* s1, const wchar_t* s2);
        wchar_t* wcsstr(      wchar_t* s1, const wchar_t* s2);

21both of which have the same behavior as the original declaration.

22The  function  signature  wmemchr(const wwchar_t_t*,  int,  size_t) is
  replaced by the two declarations:

  const wchar_t* wmemchr(const wchar_t* s, wchar_t c, size_t n);
        wchar_t* wmemchr(      wchar_t* s, wchar_t c, size_t n);

23both of which have the same behavior as the original declaration.

  SEE ALSO: ISO C subclauses 7.3, 7.10.7, 7.10.8, and  7.11.   Amendment
  1 subclauses 4.4, 4.5, and 4.6.