______________________________________________________________________

  17   Library introduction                      [lib.library]

  ______________________________________________________________________

1 This clause describes the contents of the C++ Standard library, how  a
  well-formed C++ program makes use of the library, and how a conforming
  implementation may provide the entities in the library.

2 The C++ Standard library provides an extensible  framework,  and  con­
  tains  components  for:  language support, diagnostics, general utili­
  ties, strings, locales, containers, iterators,  algorithms,  numerics,
  and  input/output.   The  language  support components are required by
  certain  parts  of  the  C++  language,  such  as  memory   allocation
  (_expr.new_, _expr.delete_) and exception processing (_except_).

3 The  general  utilities  include components used by other library ele­
  ments, such as a predefined storage allocator for dynamic storage man­
  agement  (_basic.stc.dynamic_).   The diagnostics components provide a
  consistent framework for reporting errors in a C++ program,  including
  predefined exception classes.

4 The  strings  components  provide support for manipulating text repre­
  sented as sequences of  type  char,  sequences  of  type  wchar_t,  or
  sequences of any other ``character-like'' type.  The localization com­
  ponents extend internationalization support for such text  processing.

5 The  containers,  iterators, and algorithms provide a C++ program with
  access to a subset of the most widely used algorithms and data  struc­
  tures.

6 Numeric  algorithms  and  the complex number components extend support
  for numeric processing.  The valarray components provide  support  for
  n-at-a-time processing, potentially implemented as parallel operations
  on platforms that support such processing.

7 The iostreams components are the primary  mechanism  for  C++  program
  input/output.   They  can  be used with other elements of the library,
  particularly strings, locales, and iterators.

8 This library also makes available the facilities  of  the  Standard  C
  library, suitably adjusted to ensure static type safety.

9 The following subclauses describe the definitions (_lib.definitions_),
  and method of description (_lib.description_) for the  library.   Sub­
  clause  _lib.requirements_  and Clauses _lib.language.support_ through
  _lib.input.output_ specify the contents of the  library,  and  library
  requirements  and  constraints  on  both  well-formed C++ programs and

  conforming implementations.

  17.1  Definitions                                    [lib.definitions]

  --category:  A  logical  collection  of  library  entities.    Clauses
    _lib.language.support_  through  _lib.input.output_  each describe a
    single category of entities within the library.

  --comparison function: An operator function (_over.oper_) for  any  of
    the equality (_expr.eq_) or relational (_expr.rel_) operators.

  --component:  A group of library entities directly related as members,
    parameters, or  return  types.   For  example,  the  class  template
    basic_string  and  the non-member template functions that operate on
    strings can be referred to as the string component.

  --default behavior: A description of replacement function and  handler
    function semantics.  Any specific behavior provided by the implemen­
    tation, within the scope of the required behavior.

  --handler function: A non-reserved function whose  definition  may  be
    provided  by  a  C++ program.  A C++ program may designate a handler
    function at various points in its execution, by supplying a  pointer
    to  the  function  when  calling  any  of the library functions that
    install handler functions (_lib.language.support_).

  --modifier function: A class  member  function  (_class.mfct_),  other
    than  constructors, assignment, or destructor, that alters the state
    of an object of the class.

  --object state: The current value of all nonstatic class members of an
    object  (_class.mem_).   The  state  of an object can be obtained by
    using one or more observer functions

  --observer function:  A  class  member  function  (_class.mfct_)  that
    accesses  the  state  of  an object of the class, but does not alter
    that state.  Observer functions are specified as const member  func­
    tions (_class.this_).

  --replacement  function:  A  non-reserved function whose definition is
    provided by a C++ program.  Only one definition for such a  function
    is  in  effect  for  the duration of the program's execution, as the
    result of creating the program (_lex.phases_) and resolving the def­
    initions of all translation units (_basic.link_).

  --required behavior: A description of replacement function and handler
    function semantics, applicable to both the behavior provided by  the
    implementation  and the behavior that shall be provided by any func­
    tion definition in the program.  If a function defined in a C++ pro­
    gram  fails  to  meet  the  required  behavior when it executes, the
    behavior is undefined.

  --reserved function: A function, specified as part of the C++ Standard

    library,  that must be defined by the implementation.  If a C++ pro­
    gram provides a definition for any reserved  function,  the  results
    are undefined.

    Subclause  _intro.defs_  defines  additional terms used elsewhere in
    this International Standard.

  17.2  Method of description (Informative)            [lib.description]

1 This subclause describes the conventions  used  to  describe  the  C++
  Standard  library.   It  describes  the  structures  of  the normative
  Clauses     _lib.language.support_     through      _lib.input.output_
  (_lib.structure_),      and      other      editorial      conventions
  (_lib.conventions_).

  17.2.1  Structure of each subclause                    [lib.structure]

1 Subclause _lib.organization_ provides a summary of  the  C++  Standard
  library's contents.  Other Library clauses provide detailed specifica­
  tions for each of the components in the library, as shown in Table 1:

                       Table 1--Library Categories

               +-------------------------------------------+
               |        Clause               Category      |
               +-------------------------------------------+
               |_lib.language.support_   Language support  |
               |_lib.diagnostics_        Diagnostics       |
               |_lib.utilities_          General utilities |
               |_lib.strings_            Strings           |
               |_lib.localization_       Localization      |
               |_lib.containers_         Containers        |
               |_lib.iterators_          Iterators         |
               |_lib.algorithms_         Algorithms        |
               |_lib.numerics_           Numerics          |
               |_lib.input.output_       Input/output      |
               +-------------------------------------------+

2 Each Library clause contains the following elements, as applicable:1)

  --Summary

  --Requirements

  --Detailed specifications

  --References to the Standard C library
  _________________________
  1) To save space, items that do not apply to  a  clause  are  omitted.
  For example, if a clause does not specify any requirements on template
  arguments, there will be no ``Requirements'' subclause.

  17.2.1.1  Summary                              [lib.structure.summary]

1 The Summary provides a synopsis of the category,  and  introduces  the
  first-level subclauses.  Each subclause also provides a summary, list­
  ing the headers specified in the subclause and  the  library  entities
  provided in each header.

2 Paragraphs  labelled  ``Note(s):'' or ``Example(s):'' are informative,
  other paragraphs are normative.

3 The summary and the  detailed  specifications  are  presented  in  the
  order:

  --Macros

  --Values

  --Types

  --Classes

  --Functions

  --Objects

  17.2.1.2  Requirements                    [lib.structure.requirements]

1 The  library can be extended by a C++ program.  Each clause, as appli­
  cable, describes the requirements  that  such  extensions  must  meet.
  Such extensions are generally one of the following:

  --Template arguments

  --Derived classes

  --Containers, iterators, and/or algorithms that meet an interface con­
    vention

2 The string and iostreams components use an explicit representation  of
  operations  required of template arguments.  They use a template class
  name XXX_traits to define these constraints.

3 Interface convention requirements are stated as generally as possible.
  Instead  of  stating  ``class X has to define a member function opera­
  tor++(),'' the interface requires ``for any object x of class  X,  ++x
  is  defined.''   That is, whether the operator is a member is unspeci­
  fied.

4 Requirements are stated in terms of  well-defined  expressions,  which
  define  valid  terms  of the types that satisfy the requirements.  For
  every set of requirements there is a table that specifies  an  initial
  set     of    the    valid    expressions    and    their    semantics
  (_lib.allocator.requirements_,           _lib.container.requirements_,
  _lib.iterator.requirements_).        Any       generic       algorithm

  (_lib.algorithms_) that uses the requirements is described in terms of
  the valid expressions for its formal type parameters.

5 In  some  cases  the  semantic requirements are presented as C++ code.
  Such code is intended as a specification of equivalence of a construct
  to another construct, not necessarily as the way the construct must be
  implemented.2)

  17.2.1.3  Specifications                [lib.structure.specifications]

1 The detailed specifications each contain the following elements:3)

  --Name and brief description

  --Synopsis (class definition or function prototype, as appropriate)

  --Restrictions on template arguments, if any

  --Decription of class invariants

  --Description of function semantics

2 Descriptions  of  class  member  functions  follow   the   order   (as
  appropriate):4)

  --Constructor(s) and destructor

  --Copying & assignment functions

  --Comparison functions

  --Modifier functions

  --Observer functions

  --Operators and other non-member functions

3 Descriptions  of function semantics contain the following elements (as
  appropriate):5)

  --Requires: the preconditions for calling the function
  _________________________
  2) Although in some cases the code given is unambiguously the  optimum
  implementation.
  3) The form of these specifications was designed to follow the conven­
  tions established by existing C++ library vendors.
  4) To save space, items that do not apply to a class are omitted.  For
  example, if a class does not specify any comparison  functions,  there
  will be no ``Comparison functions'' subclause.
  5) To save space, items that do not apply to a function  are  omitted.
  For  example,  if a function does not specify any preconditions, there
  will be no ``Requires'' paragraph.

  --Effects: the actions performed by the function

  --Postconditions: the observable results established by the function

  --Returns: a description of the value(s) returned by the function

  --Throws: any exceptions thrown by the function,  and  the  conditions
    that would cause the exception

  --Complexity: the time and/or space complexity of the function

4 For   non-reserved   replacement   and   handler   functions,   Clause
  _lib.language.support_ specifies two behaviors for  the  functions  in
  question:  their  required and default behavior.  The default behavior
  describes a function definition provided by the  implementation.   The
  required  behavior  describes  the  semantics of a function definition
  provided by either the implementation or a C++ program.  Where no dis­
  tinction is explicitly made in the description, the behavior described
  is the required behavior.

5 If an operation is required to be linear time, it means no worse  than
  linear  time, and a constant time operation satisfies the requirement.

  17.2.1.4  C Library                           [lib.structure.see.also]

1 Paragraphs labelled ``SEE ALSO:'' contain cross-references to the rel­
  evant  portions  of  this  Standard  and  the ISO C standard, which is
  incorporated into this Standard by reference.

  17.2.2  Other conventions                            [lib.conventions]

1 This  subclause  describes  several  editorial  conventions  used   to
  describe  the contents of the C++ Standard library.  These conventions
  are      for       describing       implementation-defined       types
  (_lib.type.descriptions_),         and         member        functions
  (_lib.functions.within.classes_).

  17.2.2.1  Type descriptions                    [lib.type.descriptions]

1 The Requirements subclauses describe names that are  used  to  specify
  constraints on template arguments.6) These names are used  in  Clauses
  _lib.containers_, _lib.algorithms_, and _lib.numerics_ to describe the
  types that may be supplied as arguments by a C++ program when  instan­
  tiating template components from the library.

2 Certain  types  defined  in  Clause  _lib.input.output_  are  used  to
  describe implementation-defined types.  They are based on other types,
  but with added constraints.

  _________________________
  6)  Examples include: InputIterator, ForwardIterator, Function, Predi­
  cate, etc.  See subclause _lib.iterator.requirements_.

  17.2.2.1.1  Enumerated types                    [lib.enumerated.types]

1 Several  types  defined  in  Clause  _lib.input.output_ are enumerated
  types.  Each enumerated type may be implemented as an  enumeration  or
  as a synonym for an enumeration.7)

2 The enumerated type enumerated can be written:
  enum enumerated { V0, V1, V2, V3, .....};

  static const enumerated C0(V0);
  static const enumerated C1(V1);
  static const enumerated C2(V2);
  static const enumerated C3(V3);
    .....

3 Here, the names C0, C1, etc.  represent enumerated elements  for  this
  particular enumerated type.  All such elements have distinct values.

  17.2.2.1.2  Bitmask types                          [lib.bitmask.types]

1 Several  types defined in Clause _lib.input.output_ are bitmask types.
  Each bitmask type can be implemented as an enumerated type that  over­
  loads   certain  operators,  as  an  integer  type,  or  as  a  bitset
  (_lib.template.bitset_).

2 The bitmask type bitmask can be written:
  enum bitmask {
    V0 = 1 << 0, V1 = 1 << 1, V2 = 1 << 2, V3 = 1 << 3, .....
  };

  static const bitmask C0(V0);
  static const bitmask C1(V1);
  static const bitmask C2(V2);
  static const bitmask C3(V3);
    .....
  bitmask& operator&=(bitmask& X, bitmask Y)      { X = bitmask(X & Y); return X; }
  bitmask& operator|=(bitmask& X, bitmask Y)      { X = bitmask(X | Y); return X; }
  bitmask& operator^=(bitmask& X, bitmask Y)      { X = bitmask(X ^ Y); return X; }
  bitmask  operator& (bitmask  X, bitmask Y)      { return bitmask(X & Y); }
  bitmask  operator| (bitmask  X, bitmask Y)      { return bitmask(X | Y); }
  bitmask  operator^ (bitmask  X, bitmask Y)      { return bitmask(X ^ Y); }
  bitmask  operator~ (bitmask  X)                 { return (bitmask)~X; }

3 Here, the names C0, C1, etc.  represent bitmask elements for this par­
  ticular  bitmask  type.   All  such elements have distinct values such
  that, for any pair Ci and Cj, Ci & Ci is nonzero and Ci & Cj is  zero.

4 The following terms apply to objects and values of bitmask types:

  _________________________
  7)  Such  as  an  integer  type,  with  constant  integer values (_ba­
  sic.fundamental_).

  --To  set  a value Y in an object X is to evaluate the expression X |=
    Y.

  --To clear a value Y in an object X is to evaluate the expression X &=
    ~Y.

  --The  value  Y  is  set  in  the  object X if the expression X & Y is
    nonzero.

  17.2.2.1.3  Character sequences                    [lib.character.seq]

1 The Standard C library makes widespread use of characters and  charac­
  ter sequences that follow a few uniform conventions:

  --A  letter  is any of the 26 lowercase or 26 uppercase letters in the
    basic execution character set.8)

  --The  decimal-point  character is the (single-byte) character used by
    functions that convert between a  (single-byte)  character  sequence
    and  a  value of one of the floating-point types.  It is used in the
    character sequence to denote the beginning of a fractional part.  It
    is    represented    in   Clauses   _lib.language.support_   through
    _lib.input.output_ by a period, '.', which is also its value in  the
    "C"  locale,  but  may  change during program execution by a call to
    setlocale(int, const char*),9) or by a change to a locale object, as
    described in Clauses _lib.locales_ and _lib.input.output_.

  --A  character sequence is an array object (_dcl.array_) A that can be
    declared as T A[N], where T is any of the types char, unsigned char,
    or  signed  char  (_basic.fundamental_), optionally qualified by any
    combination of const or volatile.  The initial elements of the array
    have  defined  contents up to and including an element determined by
    some predicate.  A character sequence can be designated by a pointer
    value S that points to its first element.

  17.2.2.1.3.1  Byte strings                          [lib.byte.strings]

1 A  null-terminated byte string, or NTBS, is a character sequence whose
  highest-addressed element with defined content has the value zero (the
  terminating null character).10)

2 The length of an NTBS is the number of elements that precede the  ter­
  minating null character.  An empty NTBS has a length of zero.

  _________________________
  8) Note that this definition differs from the definition in ISO C sub­
  clause 7.1.1.
  9) declared in <clocale> (_lib.c.locales_).
  10) Many of the objects manipulated by function signatures declared in
  <cstring> (_lib.c.strings_) are character  sequences  or  NTBSs.   The
  size  of some of these character sequences is limited by a length val­
  ue, maintained separately from the character sequence.

3 The  value  of an NTBS is the sequence of values of the elements up to
  and including the terminating null character.

4 A static NTBS is an NTBS with static storage duration.11)

  17.2.2.1.3.2  Multibyte strings                [lib.multibyte.strings]

1 A null-terminated multibyte string, or NTMBS, is an NTBS that  consti­
  tutes  a  sequence of valid multibyte characters, beginning and ending
  in the initial shift state.12)

2 A static NTMBS is an NTMBS with static storage duration.

  17.2.2.1.3.3  Wide-character sequences           [lib.wide.characters]

1 A wide-character sequence is an array object (_dcl.array_) A that  can
  be  declared  as T A[N], where T is type wchar_t (_basic.fundmental_),
  optionally qualified by any combination of  const  or  volatile.   The
  initial  elements of the array have defined contents up to and includ­
  ing an element determined by some predicate.  A character sequence can
  be  designated by a pointer value S that designates its first element.

2 A null-terminated wide-character string, or NTWCS, is a wide-character
  sequence  whose highest-addressed element with defined content has the
  value zero.13)

3 The length of an NTWCS is the number of elements that precede the ter­
  minating null wide character.  An empty NTWCS has a length of zero.

4 The value of an NTWCS is the sequence of values of the elements up  to
  and including the terminating null character.

5 A static NTWCS is an NTWCS with static storage duration.14)

  17.2.2.2  Functions within classes      [lib.functions.within.classes]

1 For the sake of  exposition,  Clauses  _lib.language.support_  through
  _lib.input.output_ do not describe copy constructors, assignment oper­
  ators, or (non-virtual) destructors with the same  apparent  semantics
  as those that can be generated by default (_class.ctor_, _class.dtor_,
  _class.copy_).

2 It is unspecified whether the implementation provides explicit defini­
  tions  for such member function signatures, or for virtual destructors
  _________________________
  11) A string literal, such as "abc", is a static NTBS.
  12) An NTBS that contains characters only  from  the  basic  execution
  character  set  is  also an NTMBS.  Each multibyte character then con­
  sists of a single byte.
  13) Many of the objects manipulated by function signatures declared in
  <cwchar> are wide-character sequences or NTWCSs.
  14) A wide string literal, such as L"abc", is a static NTWCS.

  that can be generated by default.

  17.2.2.3  Private members                 [lib.objects.within.classes]

1 Clauses _lib.language.support_ through _lib.input.output_ do not spec­
  ify  the  representation of classes, and intentionally omit specifica­
  tion of class members (_class.mem_).   An  implementation  may  define
  static  or  non-static  class members, or both, as needed to implement
  the  semantics  of  the  member   functions   specified   in   Clauses
  _lib.language.support_ through _lib.input.output_.

2 Objects  of  certain  classes  are  sometimes required by the external
  specifications of their classes to store data,  apparently  in  member
  objects.    For  the  sake  of  exposition,  subclauses  _lib.locale_,
  _lib.template.bitset_,                      _lib.istreambuf.iterator_,
  _lib.ostreambuf.iterator_,    _lib.ios.base_,   _lib.stringbuf_,   and
  _lib.filebuf_  provide  representative  declarations,   and   semantic
  requirements,  for  private  member  objects  of classes that meet the
  external specifications of the classes.   The  declarations  for  such
  member  objects  and  the  definitions  of  related  member  types are
  enclosed in a comment that ends with exposition only, as in:
          //      streambuf* sb;  exposition only

3 Any alternate implementation that provides equivalent external  behav­
  ior is equally acceptable.

  17.3  Library-wide requirements                     [lib.requirements]

1 This  subclause  specifies  requirements  that apply to the entire C++
  Standard    library.     Clauses    _lib.language.support_     through
  _lib.input.output_  specify  the  requirements  of individual entities
  within the library.

2 The following subclauses describe the library's contents and organiza­
  tion (_lib.organization_), how well-formed C++ programs gain access to
  library  entities  (_lib.using_),   constraints   on   such   programs
  (_lib.constraints_),  and  constraints  on  conforming implementations
  (_lib.conforming_).

  17.3.1  Library contents and organization           [lib.organization]

1 This subclause provides a summary of the entities defined in  the  C++
  Standard  library.   Subclause _lib.contents_ provides an alphabetical
  listing of entities by type, while subclause _lib.headers_ provides an
  alphabetical listing of library headers.

  17.3.1.1  Library contents                              [lib.contents]

1 The  C++ Standard library provides definitions for the following types
  of entities:

  --Macros

  --Values

  --Types

  --Templates

  --Classes

  --Functions

  --Objects

2 All library entities shall be defined within the namespace std.

3 The C++ Standard library  provides  54  standard  macros  from  the  C
  library (_diff.library_).

4 The  C++  Standard  library  provides  45  standard  values from the C
  library (_diff.library_).

5 The C++ Standard library provides 19 standard types from the C library
  (_diff.library_), and 28 additional types, as shown in Table 2:

                         Table 2--Standard Types

    +-----------------------------------------------------------------+
    |filebuf         ostringstream        wfilebuf         wstreambuf |
    |ifstream        streambuf            wifstream        wstreampos |
    |ios             streamoff            wios             wstring    |
    |istream         streampos            wistream         wstringbuf |
    |istringstream   string               wistringstream              |
    |new_handler     stringbuf            wofstream                   |
    |ofstream        terminate_handler    wostream                    |
    |ostream         unexpected_handler   wostringstream              |
    +-----------------------------------------------------------------+

6 The  C++  Standard  library  provides 66 standard template classes, as
  shown in Table 3:

                    Table 3--Standard Template classes

         +-------------------------------------------------------+
         |allocator               mask_array                     |
         |auto_ptr                messages                       |
         |back_insert_iterator    messages_byname                |
         |basic_filebuf           moneypunct                     |
         |basic_ifstream          moneypunct_byname              |
         |basic_ios               money_get                      |
         |basic_istream           money_put                      |
         |basic_istringstream     multimap                       |
         |basic_ofstream          multiset                       |
         |basic_ostream           numeric_limits                 |
         |basic_ostringstream     numpunct                       |
         |basic_streambuf         num_get                        |
         |basic_string            num_put                        |
         |basic_stringbuf         ostreambuf_iterator            |
         |binary_negate           ostream_iterator               |
         |binder1st               pointer_to_binary_function     |
         |binder2nd               pointer_to_unary_function      |
         |bitset                  priority_queue                 |
         |codecvt                 queue                          |
         |codecvt_byname          raw_storage_iterator           |
         |collate                 reverse_bidirectional_iterator |
         |collate_byname          reverse_iterator               |
         |complex                 set                            |
         |ctype                   slice_array                    |
         |ctype_byname            stack                          |
         |deque                   time_get                       |
         |front_insert_iterator   time_get_byname                |
         |gslice_array            time_put                       |
         |indirect_array          time_put_byname                |
         |insert_iterator         unary_negate                   |
         |istreambuf_iterator     valarray                       |
         |istream_iterator        vector                         |
         |list                                                   |
         |map                                                    |
         +-------------------------------------------------------+

7 The C++ Standard library provides 24 standard template structures,  as
  shown in Table 4:

                    Table 4--Standard Template structs

     +---------------------------------------------------------------+
     |bidirectional_iterator   less           pair                   |
     |binary_function          less_equal     plus                   |
     |divides                  logical_and    random_access_iterator |
     |equal_to                 logical_not    string_char_traits     |
     |forward_iterator         logical_or     times                  |
     |greater                  minus          unary_function         |
     |greater_equal            modulus                               |
     |input_iterator           negate                                |
     |ios_traits               not_equal_to                          |
     +---------------------------------------------------------------+

8 The  C++ Standard library provides 86 standard template operator func­
  tions, as shown in Table 5.

9 Types shown (enclosed in ( and ) ) indicate that the given function is
  overloaded  by  that type.  Numbers shown (enclosed in [ and ] ) indi­
  cate how many overloaded functions are overloaded by that type.

                   Table 5--Standard Template operators

  +--------------------------------------------------------------------+
  |operator!= (basic_string) [5]      operator<< (basic_string)        |
  |operator!= (complex)  [3]          operator<< (bitset)              |
  |operator!= (istreambuf_iterator)   operator<< (complex)             |
  |operator!= (ostreambuf_iterator)   operator<< (valarray) [3]        |
  |operator!= (T)                     operator<<=(valarray) [2]        |
  |operator!= (valarray) [3]          operator<= (T)                   |
  |operator%  (valarray) [3]          operator<= (valarray) [3]        |
  |operator%= (valarray) [2]          operator== (basic_string) [5]    |
  |operator&  (bitset)                operator== (complex)  [3]        |
  |operator&  (valarray) [3]          operator== (deque)               |
  |operator&& (valarray) [3]          operator== (istreambuf_iterator) |
  |operator&= (valarray) [2]          operator== (istream_iterator)    |
  |operator*  (complex)  [3]          operator== (list)                |
  |operator*  (valarray) [3]          operator== (map)                 |
  |operator*= (complex)               operator== (multimap)            |
  |operator*= (valarray) [2]          operator== (multiset)            |
  |operator+  (basic_string) [5]      operator== (ostreambuf_iterator) |
  |operator+  (complex)  [4]          operator== (pair)                |
  |operator+  (reverse_iterator)      operator== (queue)               |
  |operator+  (valarray) [3]          operator== (restrictor)          |
  |operator+= (complex)               operator== (reverse_bidir_iter)  |
  |operator+= (valarray) [2]          operator== (reverse_iterator)    |
  |operator-  (complex)  [4]          operator== (set)                 |
  |operator-  (reverse_iterator)      operator== (stack)               |
  |operator-  (valarray) [3]          operator== (valarray) [3]        |
  |operator-= (complex)               operator== (vector)              |
  |operator-= (valarray) [2]          operator>  (T)                   |
  |operator/  (complex)  [3]          operator>  (valarray) [3]        |
  |operator/  (valarray) [3]          operator>= (T)                   |
  |operator/= (complex)               operator>= (valarray) [3]        |
  |operator/= (valarray) [2]          operator>> (basic_string)        |
  |operator<  (deque)                 operator>> (bitset)              |
  |operator<  (list)                  operator>> (complex)             |
  |operator<  (map)                   operator>> (valarray) [3]        |
  |operator<  (multimap)              operator>>=(valarray) [2]        |
  |operator<  (multiset)              operator^  (bitset)              |
  |operator<  (pair)                  operator^  (valarray) [3]        |
  |operator<  (queue)                 operator^= (valarray) [2]        |
  |operator<  (restrictor)            operator|  (bitset)              |
  |operator<  (reverse_iterator)      operator|  (valarray) [3]        |
  |operator<  (set)                   operator|= (valarray) [2]        |
  |operator<  (stack)                 operator|| (valarray) [3]        |
  |operator<  (valarray) [3]                                           |
  |operator<  (vector)                                                 |
  +--------------------------------------------------------------------+

10The C++ Standard library provides 144 standard template functions,  as
  shown in Table 6:

                   Table 6--Standard Template functions

   +-------------------------------------------------------------------+
   |abs  (complex)                        lower_bound [2]              |
   |abs  (valarray)                       make_heap [2]                |
   |accumulate [2]                        make_pair                    |
   |acos (complex)                        max [2]                      |
   |acos (valarray)                       max_element [2]              |
   |adjacent_difference [2]               merge [2]                    |
   |adjacent_find [2]                     min [2]                      |
   |advance                               min_element [2]              |
   |allocate                              mismatch [2]                 |
   |arg  (complex)                        next_permutation [2]         |
   |asin (complex)                        norm (complex)               |
   |asin (valarray)                       not1                         |
   |atan (complex)                        not2                         |
   |atan (valarray)                       nth_element [2]              |
   |atan2(complex) [3]                    partial_sort [2]             |
   |atan2(valarray) [3]                   partial_sort_copy [2]        |
   |back_inserter                         partial_sum [2]              |
   |binary_search [2]                     partition                    |
   |bind1st                               polar(complex)               |
   |bind2nd                               pop_heap [2]                 |
   |conj (complex)                        pow  (complex)               |
   |construct                             pow  (complex) [3]           |
   |copy                                  pow  (valarray) [3]          |
   |copy_backward                         prev_permutation [2]         |
   |cos  (complex)                        ptr_fun [2]                  |
   |cos  (valarray)                       push_heap [2]                |
   |cosh (complex)                        random_shuffle [2]           |
   |cosh (valarray)                       real (complex)               |
   |count                                 remove                       |
   |count_if                              remove_copy                  |
   |deallocate                            remove_copy_if               |
   |destroy [2]                           remove_if                    |
   |distance                              replace                      |
   |distance_type (istreambuf_iterator)   replace_copy                 |
   |distance_type [5]                     replace_copy_if              |
   |equal [2]                             replace_if                   |
   |equal_range [2]                       reverse                      |
   |exp  (complex)                        reverse_copy                 |
   |exp  (valarray)                       rotate                       |
   |fill                                  rotate_copy                  |
   |fill_n                                search [4]                   |
   |find                                  set_difference [2]           |
   |find_end [4]                          set_intersection [2]         |
   |find_first_of [2]                     set_symmetric_difference [2] |
   |find_if                               set_union [2]                |
   +-------------------------------------------------------------------+

           +---------------------------------------------------+
           |for_each                      sin  (complex)       |
           |front_inserter                sin  (valarray)      |
           |generate                      sinh (complex)       |
           |generate_n                    sinh (valarray)      |
           |getline                       sort [2]             |
           |get_temporary_buffer          sort_heap [2]        |
           |imag (complex)                sqrt (complex)       |
           |includes [2]                  sqrt (valarray)      |
           |inner_product [2]             stable_partition     |
           |inplace_merge [2]             stable_sort [2]      |
           |inserter                      swap                 |
           |isalnum                       swap_ranges          |
           |isalpha                       tan  (complex)       |
           |iscntrl                       tan  (valarray)      |
           |isdigit                       tanh (complex)       |
           |isgraph                       tanh (valarray)      |
           |islower                       tolower              |
           |isprint                       toupper              |
           |ispunct                       transform [2]        |
           |isspace                       uninitialized_copy   |
           |isupper                       uninitialized_fill   |
           |isxdigit                      uninitialized_fill_n |
           |iterator_category [7]         unique [2]           |
           |lexicographical_compare [2]   unique_copy [2]      |
           |log  (complex)                upper_bound [2]      |
           |log  (valarray)               value_type [7]       |
           |log10(complex)                                     |
           |log10(valarray)                                    |
           +---------------------------------------------------+

11The  C++  Standard  library  provides 28 standard classes, as shown in
  Table 7.

12Type names (enclosed in < and > ) indicate  that  these  are  specific
  instances of templates.

                        Table 7--Standard Classes

  +--------------------------------------------------------------------+
  |bad_alloc               ctype_byname<char>   logic_error            |
  |bad_cast                domain_error         out_of_range           |
  |bad_exception           exception            overflow_error         |
  |bad_typeid              gslice               range_error            |
  |basic_string<char>      invalid_argument     runtime_error          |
  |basic_string<wchar_t>   ios_base             slice                  |
  |complex<double>         length_error         type_info              |
  |complex<float>          locale               vector<bool,allocator> |
  |complex<long double>    locale::facet                               |
  |ctype<char>             locale::id                                  |
  +--------------------------------------------------------------------+

13The  C++  Standard  library  provides 2 standard structures from the C
  library (_diff.library_), and 16 additional structures,  as  shown  in
  Table 8:

                        Table 8--Standard Structs

        +---------------------------------------------------------+
        |bidirectional_iterator_tag   nothrow                     |
        |codecvt_base                 output_iterator             |
        |ctype_base                   output_iterator_tag         |
        |forward_iterator_tag         random_access_iterator_tag  |
        |input_iterator_tag           string_char_traits<char>    |
        |ios_traits<char>             string_char_traits<wchar_t> |
        |ios_traits<wchar_t>          time_base                   |
        |money_base                                               |
        |money_base::pattern                                      |
        +---------------------------------------------------------+

14The  C++  Standard library provides 12 standard operator functions, as
  shown in Table 9:

                   Table 9--Standard Operator functions

     +---------------------------------------------------------------+
     |operator delete            operator new[] (void*)              |
     |operator delete[]          operator<  (vector<bool,allocator>) |
     |operator new               operator<< (locale)                 |
     |operator new (nothrow)     operator== (vector<bool,allocator>) |
     |operator new (void*)       operator>> (locale)                 |
     |operator new[]                                                 |
     |operator new[] (nothrow)                                       |
     +---------------------------------------------------------------+

15The C++ Standard library provides 208 standard functions  from  the  C
  library  (_diff.library_),  and  78  additional functions, as shown in
  Table 10:

                       Table 10--Standard Functions

    +-----------------------------------------------------------------+
    |abs  (float)                     mod  (long double)              |
    |abs  (long double)               modf (float,float*)             |
    |abs  (long)                      modf (long double,long double*) |
    |acos (float)                     noshowbase                      |
    |acos (long double)               noshowpoint                     |
    |asin (float)                     noshowpos                       |
    |asin (long double)               noskipws                        |
    |atan (float)                     nouppercase                     |
    |atan (long double)               oct                             |
    |atan2(float,float)               pow  (float) [2]                |
    |atan2(long double,long double)   pow  (long double) [2]          |
    |ceil (float)                     resetiosflags                   |
    |ceil (long double)               right                           |
    |cos  (float)                     scientific                      |
    |cos  (long double)               setbase                         |
    |cosh (float)                     setfill                         |
    |cosh (long double)               setiosflags                     |
    |dec                              setprecision                    |
    |div  (long,long)                 setw                            |
    |endl                             set_new_handler                 |
    |ends                             set_terminate                   |
    |exp  (float)                     set_unexpected                  |
    |exp  (long double)               showbase                        |
    |fixed                            showpoint                       |
    |floor(float)                     showpos                         |
    |floor(long double)               sin  (float)                    |
    |flush                            sin  (long double)              |
    |frexp(float,int*)                sinh (float)                    |
    |frexp(long double,int*)          sinh (long double)              |
    |hex                              skipws                          |
    |internal                         tan  (float)                    |
    |iterator_category                tan  (long double)              |
    |ldexp(float,int)                 tanh (float)                    |
    |ldexp(long double,int)           tanh (long double)              |
    |left                             terminate                       |
    |log  (float)                     unexpected                      |
    |log  (long double)               uppercase                       |
    |log10(float)                     ws                              |
    |log10(long double)                                               |
    |mod  (float)                                                     |
    +-----------------------------------------------------------------+

16The C++ Standard library provides 8  standard  objects,  as  shown  in
  Table 11:

                        Table 11--Standard Objects

                        +-------------------------+
                        |cerr   cin   clog   cout |
                        |werr   win   wlog   wout |
                        +-------------------------+

  17.3.1.2  Headers                                        [lib.headers]

1 The  elements  of the C++ Standard library are declared or defined (as
  appropriate) in a header.15)

2 The C++ Standard library provides 32 C++ headers, as  shown  in  Table
  12:

                      Table 12--C++ Library Headers

    +-----------------------------------------------------------------+
    |<algorithm>    <iomanip>    <list>      <queue>       <typeinfo> |
    |<bitset>       <ios>        <locale>    <set>         <utility>  |
    |<complex>      <iosfwd>     <map>       <sstream>     <valarray> |
    |<deque>        <iostream>   <memory>    <stack>       <vector>   |
    |<exception>    <istream>    <new>       <stdexcept>              |
    |<fstream>      <iterator>   <numeric>   <streambuf>              |
    |<functional>   <limits>     <ostream>   <string>                 |
    +-----------------------------------------------------------------+

3 The facilities of the Standard C Library are provided in 18 additional
  headers, as shown in Table 13:

              Table 13--C++ Headers for C Library Facilities

            +-------------------------------------------------+
            |<cassert> <csetjmp> <cstdio>  <cwchar>  <cctype> |
            |<climits> <csignal> <cstdlib> <cwctype> <cerrno> |
            |<clocale> <cstdarg> <cstring> <cfloat>  <cmath>  |
            |<cstddef> <ctime>                                |
            +-------------------------------------------------+

4 Except   as   noted   in   Clauses   _lib.language.support_    through
  _lib.input.output_,  the  contents  of  each header cname shall be the
  _________________________
  15) A header is not necessarily a source file, nor are  the  sequences
  delimited  by  <  and  > in header names necessarily valid source file
  names (_cpp.include_).

  same as that of the corresponding header name.h, as specified in ISO C
  (Clause  7),  or Amendment 1, (Clause 7), as appropriate.  In this C++
  Standard library, however, the declarations and definitions are within
  namespace scope (_basic.scope.namespace_) of the namespace std.

5 Subclause  _depr.c.headers_, Standard C library headers, describes the
  effects of using the name.h (C header) form in a C++ program.16)

  17.3.1.3  Freestanding implementations                [lib.compliance]

1 Two  kinds  of  implementations  are  defined: hosted and freestanding
  (_intro.compliance_).  For a hosted implementation, this International
  Standard describes the set of available headers.

2 A freestanding implementation has has an implementation-defined set of
  headers.  This set shall include at least the  following  headers,  as
  shown in Table 14:

          Table 14--C++ Headers for Freestanding Implementations

     +--------------------------------------------------------------+
     |                   Subclause                       Header(s)  |
     +--------------------------------------------------------------+
     |_lib.support.types_ Types                         <cstddef>   |
     +--------------------------------------------------------------+
     |_lib.support.limits_ Implementation properties    <limits>    |
     +--------------------------------------------------------------+
     |_lib.support.start.term_ Start and termination    <cstdlib>   |
     +--------------------------------------------------------------+
     |_lib.support.dynamic_ Dynamic memory management   <new>       |
     +--------------------------------------------------------------+
     |_lib.support.rtti_ Type identification            <typeinfo>  |
     +--------------------------------------------------------------+
     |_lib.support.exception_ Exception handling        <exception> |
     +--------------------------------------------------------------+
     |_lib.support.runtime_ Other runtime support       <cstdarg>   |
     +--------------------------------------------------------------+

3 The  supplied  version  of the header <cstdlib> shall declare at least
  the      functions      abort(),      atexit(),       and       exit()
  (_lib.support.start.term_).

  _________________________
  16) The ".h" headers dump all their names into the  global  namespace,
  whereas the newer forms keep their names in namespace std.  Therefore,
  the newer forms are the preferred forms for all uses  except  for  C++
  programs which are intended to be strictly compatible with C.

  17.3.2  Using the library                                  [lib.using]

1 This subclause describes how a C++ program gains access to the facili­
  ties of  the  C++  Standard  library.   Subclause  _lib.using.headers_
  describes   effects   during  translation  phase  4,  while  subclause
  _lib.using.linkage_ describes effects during phase 8 (_lex.phases_).

  17.3.2.1  Headers                                  [lib.using.headers]

1 The entities in the C++ Standard library are defined in headers, whose
  contents are made available to a translation unit when it contains the
  appropriate #include preprocessing directive (_cpp.include_).

2 A translation unit may include library headers in any  order  (_lex_).
  Each  may  be  included  more than once, with no effect different from
  being included exactly once,  except  that  the  effect  of  including
  either <cassert> or <assert.h> depends each time on the lexically cur­
  rent definition of NDEBUG.17)

3 A translation unit shall include a header only outside of any external
  declaration  or  definition,  and  shall  include the header lexically
  before the first reference to any of the entities it declares or first
  defines in that translation unit.

  17.3.2.2  Linkage                                  [lib.using.linkage]

1 Entities   in   the   C++   Standard  library  have  external  linkage
  (_basic.link_).  Unless otherwise  specified,  objects  and  functions
  have the default extern "C++" linkage (_dcl.link_).

2 It  is unspecified whether a name from the Standard C library declared
  with  external  linkage  has  either  extern  "C"  or   extern   "C++"
  linkage.18)

3 Objects and functions defined in the library and  required  by  a  C++
  program are included in the program prior to program startup.

  SEE ALSO:  replacement  functions  (_lib.replacement.functions_), run-
  time changes (_lib.handler.functions_).

  17.3.3  Constraints on programs                      [lib.constraints]

1 This subclause describes restrictions on C++  programs  that  use  the
  facilities  of  the  C++  Standard  library.  The following subclauses
  specify constraints on the program's namespace (_lib.reserved.names_),
  its  use of headers (_lib.alt.headers_), classes derived from standard
  _________________________
  17) This is the same as the Standard C library.
  18)  The  only reliable way to declare an object or function signature
  from the Standard C library is by including the header  that  declares
  it,  notwithstanding  the latitude granted in subclause 7.1.7 of the C
  Standard.

  library classes (_lib.derived.classes_),  definitions  of  replacement
  functions  (_lib.replacement.functions_),  and installation of handler
  functions during execution (_lib.handler.functions_).

  17.3.3.1  Reserved names                          [lib.reserved.names]

1 A C++ program shall not extend the namespace std.

  +-------                 BEGIN BOX 1                -------+
  ISSUE: This topic needs further discussion.

  For example, implementation names could be required to be in  a  sepa­
  rate std::__implementation namespace.
  +-------                  END BOX 1                 -------+

2 The C++ Standard library reserves the following kinds of names:

  --Macros

  --Global names

  --Names with external linkage

3 If  the  program  declares  or defines a name in a context where it is
  reserved, other than as explicitly allowed by this clause, the  behav­
  ior is undefined.

  17.3.3.1.1  Macro names                              [lib.macro.names]

1 Each  name defined as a macro in a header is reserved to the implemen­
  tation for any use if the translation unit includes the header.19)

2 A translation unit that includes a header shall not contain any macros
  that define names declared or defined in that header.  Nor shall  such
  a translation unit define macros for names lexically identical to key­
  words.

  17.3.3.1.2  Global names                            [lib.global.names]

1 Each header also optionally declares or defines names which are always
  reserved  to  the implementation for any use and names reserved to the
  implementation for use at file scope.

2 Certain sets of names and function signatures are reserved whether  or
  not a translation unit includes a header:

3 Each  name that begins with an underscore and either an uppercase let­
  ter  or  another   underscore   (_lex.key_)   is   reserved   to   the
  _________________________
  19) It is not permissible to remove a library macro definition by  us­
  ing the #undef directive.

  implementation for any use.

4 Each  name that begins with an underscore is reserved to the implemen­
  tation for use as a name with file scope or within the  namespace  std
  in the ordinary name space.

  17.3.3.1.3  External linkage                        [lib.extern.names]

1 Each  name  declared as an object with external linkage in a header is
  reserved to the implementation to designate that library  object  with
  external linkage.20)

2 Each global function signature declared with  external  linkage  in  a
  header  is  reserved  to the implementation to designate that function
  signature with external linkage.21)

3 Each name having two consecutive underscores (_lex.key_)  is  reserved
  to  the  implementation  for  use  as  a name with both extern "C" and
  extern "C++" linkage.

4 Each name from the Standard C library declared with  external  linkage
  is  reserved  to  the implementation for use as a name with extern "C"
  linkage.

5 Each function signature from the  Standard  C  library  declared  with
  external  linkage is reserved to the implementation for use as a func­
  tion signature with both extern "C" and extern "C++" linkage.22)

  17.3.3.2  Headers                                    [lib.alt.headers]

1 If a file with a name equivalent to the derived file name for  one  of
  the C++ Standard library headers is not provided as part of the imple­
  mentation, and a file with that name is placed in any of the  standard
  places  for a source file to be included (_cpp.include_), the behavior
  is undefined.

  17.3.3.3  Derived classes                        [lib.derived.classes]

1 Virtual member function signatures defined for a base class in the C++
  Standard  library  may be overridden in a derived class defined in the
  program (_class.virtual_).

  _________________________
  20)  The  list  of such reserved names includes errno, declared or de­
  fined in <cerrno>.
  21) The list of such reserved function signatures with external  link­
  age  includes  setjmp(jmp_buf),  declared or defined in <csetjmp>, and
  va_end(va_list), declared or defined in <cstdarg>.
  22) The function signatures declared in <cwchar> and <cwctype> are al­
  ways  reserved,  notwithstanding the restrictions imposed in subclause
  4.5.1 of Amendment 1 to the C Standard for these headers.

  17.3.3.4  Replacement functions            [lib.replacement.functions]

1 Clauses _lib.language.support_ through _lib.input.output_ describe the
  behavior  of  numerous  functions defined by the C++ Standard library.
  Under some circumstances, however, certain of these function  descrip­
  tions  also  apply  to  replacement  functions  defined in the program
  (_lib.definitions_).

2 A C++ program may provide the definition for any of  six  (6)  dynamic
  memory   allocation  function  signatures  declared  in  header  <new>
  (_basic.stc.dynamic_, _lib.language.support_):

  --operator new(size_t)

  --operator new(size_t,nothrow)

  --operator new[](size_t)

  --operator new[](size_t,nothrow)

  --operator delete(void*)

  --operator delete[](void*)

3 The program's definitions are used instead  of  the  default  versions
  supplied  by  the  implementation  (_dcl.fct.def_).   Such replacement
  occurs prior to program startup (_basic.def.odr_, _basic.start_).

  17.3.3.5  Handler functions                    [lib.handler.functions]

1 The C++ Standard library provides default versions of the  three  han­
  dler functions (_lib.language.support_):

  --new_handler

  --unexpected_handler

  --terminate_handler

2 A  C++  program  may install different handler functions during execu­
  tion, by supplying a pointer to a function defined in the  program  or
  the library as an argument to (respectively):

  --set_new_handler

  --set_unexpected

  --set_terminate

  SEE ALSO:  subclauses  _lib.alloc.errors_,  Storage allocation errors,
  and _lib.support.exception_, Exception handling.

  17.3.3.6  Other functions                       [lib.res.on.functions]

1 In certain cases (replacement functions, handler functions, operations
  on  types  used  to instantiate standard library template components),
  the C++ Standard library depends on components supplied by a C++  pro­
  gram.   If  these components do not meet their requirements, the Stan­
  dard places no requirements on the implementation.

2 In particular, the effects are undefined in the following cases:

  --for replacement functions (_lib.new.delete_), if the installed  han­
    dler  function  does  not  implement the semantics of the applicable
    Required behavior paragraph.

  --for handler functions  (_lib.new.handler_,  _lib.terminate.handler_,
    _lib.unexpected.handler_),  if  the  installed handler function does
    not implement the semantics  of  the  applicable  Required  behavior
    paragraph

  --for  types  used as template arguments when instantiating a template
    component, if the operations on the type do not implement the seman­
    tics      of      the      applicable     Requirements     subclause
    (_lib.allocator.requirements_,         _lib.container.requirements_,
    _lib.iterator.requirements_, _lib.numeric.requirements_).

  --if  any of these functions or operations throws an exception, unless
    specifically allowed in the applicable Required behavior  paragraph.

  17.3.3.7  Function arguments                    [lib.res.on.arguments]

1 Each of the following statements applies to all arguments to functions
  defined in the C++ Standard library, unless explicitly  stated  other­
  wise.

  --If  an  argument to a function has an invalid value (such as a value
    outside the domain of the function, or a  pointer  invalid  for  its
    intended use), the behavior is undefined.

  --If  a  function argument is described as being an array, the pointer
    actually passed to the function shall have a  value  such  that  all
    address computations and accesses to objects (that would be valid if
    the pointer did point to the first element of such an array) are  in
    fact valid.

  17.3.4  Conforming implementations                    [lib.conforming]

1 This subclause describes the constraints upon, and latitude of, imple­
  mentations of the C++  Standard  library.   The  following  subclauses
  describe  an  implementation's  use of headers (_lib.res.on.headers_),
  macros     (_lib.res.on.macro.definitions_),     global      functions
  (_lib.global.functions_),  member  functions (_lib.member.functions_),
  reentrancy        (_lib.reentrancy_),        access         specifiers
  (_lib.protection.within.classes_),           class          derivation

  (_lib.derivation_), and exceptions  (_lib.res.on.exception.handling_).

  17.3.4.1  Headers                                 [lib.res.on.headers]

1 Certain  types  and  macros  are defined in more than one header.  For
  such an entity, a second or subsequent header that also defines it may
  be  included  after  the  header  that provides its initial definition
  (_basic.def.odr_).

2 Header inclusion is limited as follows:

  --The C headers ( .h form, described  in  Annex  D,  _depr.c.headers_)
    shall  include  only  their  corresponding  C++ header, as described
    above (_lib.headers_).

  --The C++ headers listed in  Table  21,  C++  Library  Headers,  shall
    include  the header(s) listed in their respective Synopsis subclause
    (_lib.support.dynamic_, _lib.support.rtti_, _lib.support.exception_,
    _lib.std.exceptions_,     _lib.utility_,     _lib.function.objects_,
    _lib.memory_, _lib.string.classes_, _lib.locales_,  _lib.sequences_,
    _lib.iterators_,       _lib.algorithms_,      _lib.complex.numbers_,
    _lib.numarray_,    _lib.iostream.objects_,     _lib.iostreams.base_,
    _lib.stream.buffers_,  _lib.iostream.format_,  _lib.string.streams_,
    _lib.fstreams_).23)

  +-------                 BEGIN BOX 2                -------+
  Change:  This appeared as an Editorial proposal in the April 1995 edi­
  tion.
  +-------                  END BOX 2                 -------+

  17.3.4.2  Restrictions on macro         [lib.res.on.macro.definitions]
       definitions

1 The  names  or  global  function  signatures  described  in  subclause
  _lib.contents_ are reserved to the implementation.24)

2 All object-like macros defined by the Standard C library and described
  in this clause as expanding to integral constant expressions are  also
  suitable  for  use  in #if preprocessing directives, unless explicitly
  stated otherwise.

  _________________________
  23) C++ headers must include a C++ header  that  contains  any  needed
  definition (_basic.def.odr_).
  24) A global function cannot be declared by the implementation as tak­
  ing additional default arguments.  Also, the use of masking macros for
  function signatures declared in C headers is disallowed, notwithstand­
  ing  the  latitude  granted in subclause 7.1.7 of the C Standard.  The
  use of a masking macro can often be replaced by defining the  function
  signature as inline.

  17.3.4.3  Global functions                      [lib.global.functions]

1 It is unspecified whether any global functions  in  the  C++  Standard
  library are defined as inline (_dcl.fct.spec_).

2 A   call   to   a  global  function  signature  described  in  Clauses
  _lib.language.support_ through _lib.input.output_ behaves the same  as
  if   the   implementation   declares  no  additional  global  function
  signatures.25)

  17.3.4.4  Member functions                      [lib.member.functions]

1 It is unspecified whether any member functions  in  the  C++  Standard
  library are defined as inline (_dcl.fct.spec_).

2 An  implementation  can declare additional non-virtual member function
  signatures within a class:

  --by adding  arguments  with  default  values  to  a  member  function
    signature;26) The same latitude does not extend to  the  implementa­
    tion of virtual or global functions, however.

  --by  replacing a member function signature with default values by two
    or more member function signatures with equivalent behavior;

  --by adding a member function signature for a member function name.

3 A call to a member function signature described in  the  C++  Standard
  library  behaves  the  same as if the implementation declares no addi­
  tional member function signatures.27)

  17.3.4.5  Reentrancy                                  [lib.reentrancy]

1 Which  of  the functions in the C++ Standard Library are not reentrant
  subroutines is implementation-defined.

  17.3.4.6  Protection within            [lib.protection.within.classes]
       classes

1 It  is  unspecified whether a function signature or class described in
  Clauses _lib.language.support_ through _lib.input.output_ is a  friend
  of another class in the C++ Standard Library.
  _________________________
  25) A valid C++ program always calls the expected library global func­
  tion.   An  implementation may also define additional global functions
  that would otherwise not be called by a valid C++ program.
  26)  Hence, taking the address of a member function has an unspecified
  type.
  27) A valid C++ program always calls the expected library member func­
  tion, or one with equivalent behavior.  An implementation may also de­
  fine additional member functions that would otherwise not be called by
  a valid C++ program.

  +-------                 BEGIN BOX 3                -------+
  Change:  This appeared as an Editorial proposal in the April 1995 edi­
  tion.
  +-------                  END BOX 3                 -------+

  17.3.4.7  Derived classes                             [lib.derivation]

1 Certain classes defined in the C++ Standard Library are  derived  from
  other classes in the C++ Standard library:

  --It  is  unspecified whether a class in the C++ Standard Library as a
    base class is itself derived from other  base  classes  (with  names
    reserved to the implementation).

  --It  is  unspecified  whether  a  class described in the C++ Standard
    Library as derived from another class is  derived  from  that  class
    directly,  or  through  other  classes  (with  names reserved to the
    implementation) that are derived from the specified base class.

2 In any case:

  --A base class described as virtual is always virtual;

  --A base class described as non-virtual is never virtual;

  --Unless explicitly stated otherwise, types with  distinct  names  are
    distinct types.28)

  17.3.4.8  Restrictions on              [lib.res.on.exception.handling]
       exception handling

1 Any of the functions defined in the C++ Standard library can report  a
  failure  by  throwing  an  exception of the type(s) described in their
  Throws:     paragraph     and/or     their     exception-specification
  (_except.spec_).   An  implementation  may  strengthen  the exception-
  specification for a function by removing listed exceptions.29)

2 None of the functions from the Standard  C  library  shall  report  an
  error  by throwing an exception,30) unless it calls a program-supplied
  _________________________
  28) An implicit exception to this rule are types described as synonyms
  for basic integral types, such  as  size_t  (_lib.support.types_)  and
  streamoff (_lib.stream.types_).
  29) That is, an implementation of the function will have  an  explicit
  exception-specification  that lists fewer exceptions than those speci­
  fied in this International Standard.  It may not, however, change  the
  types  of  exceptions listed in the exception-specficiation from those
  specified, nor add others.
  30)  That  is,  the  C library functions all have a throw() exception-
  specification.  This allows implementations to make performance  opti­
  mizations based on the absence of exceptions at runtime.

  function that throws an exception.31)

3 Any  of  the functions defined in the C++ Standard library that do not
  have an exception-specification may throw any exception.32) An  imple­
  mentation  may  strengthen  this  implicit  exception-specification by
  adding an explicit one.33)

  _________________________
  31) The functions qsort()  and  bsearch()  (_lib.alg.c.library_)  meet
  this condition.
  32) In particular, they can report a failure to  allocate  storage  by
  throwing  an  exception  of  type  bad_alloc,  or a class derived from
  bad_alloc (_lib.bad.alloc_).
  33) That is, an implementation  may  provide  an  explicit  exception-
  specification  that defines the subset of ``any'' exceptions thrown by
  that function.  This implies that the implementation may  list  imple­
  mentation-defined types in such an exception-specification.