Imported Upstream version 1.49.0upstream/1.49.0

1 files changed, 1761 insertions, 0 deletions

diff --git a/boost/dynamic_bitset/dynamic_bitset.hpp b/boost/dynamic_bitset/dynamic_bitset.hpp
new file mode 100644
index 0000000000..930e4b2dab
--- /dev/null
+++ b/boost/dynamic_bitset/dynamic_bitset.hpp
@@ -0,0 +1,1761 @@
+// -----------------------------------------------------------
+//
+//   Copyright (c) 2001-2002 Chuck Allison and Jeremy Siek
+//        Copyright (c) 2003-2006, 2008 Gennaro Prota
+//
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+//
+// -----------------------------------------------------------
+
+#ifndef BOOST_DYNAMIC_BITSET_DYNAMIC_BITSET_HPP
+#define BOOST_DYNAMIC_BITSET_DYNAMIC_BITSET_HPP
+
+#include <assert.h>
+#include <string>
+#include <stdexcept>
+#include <algorithm>
+#include <vector>
+#include <climits>      // for CHAR_BIT
+
+#include "boost/dynamic_bitset/config.hpp"
+
+#ifndef BOOST_NO_STD_LOCALE
+#  include <locale>
+#endif
+
+#if defined(BOOST_OLD_IOSTREAMS)
+#  include <iostream.h>
+#  include <ctype.h> // for isspace
+#else
+#  include <istream>
+#  include <ostream>
+#endif
+
+#include "boost/dynamic_bitset_fwd.hpp"
+#include "boost/detail/dynamic_bitset.hpp"
+#include "boost/detail/iterator.hpp" // used to implement append(Iter, Iter)
+#include "boost/static_assert.hpp"
+#include "boost/limits.hpp"
+#include "boost/pending/lowest_bit.hpp"
+
+
+namespace boost {
+
+template <typename Block, typename Allocator>
+class dynamic_bitset
+{
+  // Portability note: member function templates are defined inside
+  // this class definition to avoid problems with VC++. Similarly,
+  // with the member functions of nested classes.
+  //
+  // [October 2008: the note above is mostly historical; new versions
+  // of VC++ are likely able to digest a more drinking form of the
+  // code; but changing it now is probably not worth the risks...]
+
+  BOOST_STATIC_ASSERT((bool)detail::dynamic_bitset_impl::allowed_block_type<Block>::value);
+
+public:
+    typedef Block block_type;
+    typedef Allocator allocator_type;
+    typedef std::size_t size_type;
+    typedef block_type block_width_type;
+
+    BOOST_STATIC_CONSTANT(block_width_type, bits_per_block = (std::numeric_limits<Block>::digits));
+    BOOST_STATIC_CONSTANT(size_type, npos = static_cast<size_type>(-1));
+
+
+public:
+
+    // A proxy class to simulate lvalues of bit type.
+    //
+    class reference
+    {
+        friend class dynamic_bitset<Block, Allocator>;
+
+
+        // the one and only non-copy ctor
+        reference(block_type & b, block_type pos)
+            :m_block(b),
+             m_mask( (assert(pos < bits_per_block),
+                      block_type(1) << pos )
+                   )
+        { }
+
+        void operator&(); // left undefined
+
+    public:
+
+        // copy constructor: compiler generated
+
+        operator bool() const { return (m_block & m_mask) != 0; }
+        bool operator~() const { return (m_block & m_mask) == 0; }
+
+        reference& flip() { do_flip(); return *this; }
+
+        reference& operator=(bool x)               { do_assign(x);   return *this; } // for b[i] = x
+        reference& operator=(const reference& rhs) { do_assign(rhs); return *this; } // for b[i] = b[j]
+
+        reference& operator|=(bool x) { if  (x) do_set();   return *this; }
+        reference& operator&=(bool x) { if (!x) do_reset(); return *this; }
+        reference& operator^=(bool x) { if  (x) do_flip();  return *this; }
+        reference& operator-=(bool x) { if  (x) do_reset(); return *this; }
+
+     private:
+        block_type & m_block;
+        const block_type m_mask;
+
+        void do_set() { m_block |= m_mask; }
+        void do_reset() { m_block &= ~m_mask; }
+        void do_flip() { m_block ^= m_mask; }
+        void do_assign(bool x) { x? do_set() : do_reset(); }
+    };
+
+    typedef bool const_reference;
+
+    // constructors, etc.
+    explicit
+    dynamic_bitset(const Allocator& alloc = Allocator());
+
+    explicit
+    dynamic_bitset(size_type num_bits, unsigned long value = 0,
+               const Allocator& alloc = Allocator());
+
+
+    // WARNING: you should avoid using this constructor.
+    //
+    //  A conversion from string is, in most cases, formatting,
+    //  and should be performed by using operator>>.
+    //
+    // NOTE:
+    //  Leave the parentheses around std::basic_string<CharT, Traits, Alloc>::npos.
+    //  g++ 3.2 requires them and probably the standard will - see core issue 325
+    // NOTE 2:
+    //  split into two constructors because of bugs in MSVC 6.0sp5 with STLport
+
+    template <typename CharT, typename Traits, typename Alloc>
+    dynamic_bitset(const std::basic_string<CharT, Traits, Alloc>& s,
+        typename std::basic_string<CharT, Traits, Alloc>::size_type pos,
+        typename std::basic_string<CharT, Traits, Alloc>::size_type n,
+        size_type num_bits = npos,
+        const Allocator& alloc = Allocator())
+
+    :m_bits(alloc),
+     m_num_bits(0)
+    {
+      init_from_string(s, pos, n, num_bits);
+    }
+
+    template <typename CharT, typename Traits, typename Alloc>
+    explicit
+    dynamic_bitset(const std::basic_string<CharT, Traits, Alloc>& s,
+      typename std::basic_string<CharT, Traits, Alloc>::size_type pos = 0)
+
+    :m_bits(Allocator()),
+     m_num_bits(0)
+    {
+      init_from_string(s, pos, (std::basic_string<CharT, Traits, Alloc>::npos),
+                       npos);
+    }
+
+    // The first bit in *first is the least significant bit, and the
+    // last bit in the block just before *last is the most significant bit.
+    template <typename BlockInputIterator>
+    dynamic_bitset(BlockInputIterator first, BlockInputIterator last,
+                   const Allocator& alloc = Allocator())
+
+    :m_bits(alloc),
+     m_num_bits(0)
+    {
+        using boost::detail::dynamic_bitset_impl::value_to_type;
+        using boost::detail::dynamic_bitset_impl::is_numeric;
+
+        const value_to_type<
+            is_numeric<BlockInputIterator>::value> selector;
+
+        dispatch_init(first, last, selector);
+    }
+
+    template <typename T>
+    void dispatch_init(T num_bits, unsigned long value,
+                       detail::dynamic_bitset_impl::value_to_type<true>)
+    {
+        init_from_unsigned_long(static_cast<size_type>(num_bits), value);
+    }
+
+    template <typename T>
+    void dispatch_init(T first, T last,
+                       detail::dynamic_bitset_impl::value_to_type<false>)
+    {
+        init_from_block_range(first, last);
+    }
+
+    template <typename BlockIter>
+    void init_from_block_range(BlockIter first, BlockIter last)
+    {
+        assert(m_bits.size() == 0);
+        m_bits.insert(m_bits.end(), first, last);
+        m_num_bits = m_bits.size() * bits_per_block;
+    }
+
+    // copy constructor
+    dynamic_bitset(const dynamic_bitset& b);
+
+    ~dynamic_bitset();
+
+    void swap(dynamic_bitset& b);
+    dynamic_bitset& operator=(const dynamic_bitset& b);
+
+    allocator_type get_allocator() const;
+
+    // size changing operations
+    void resize(size_type num_bits, bool value = false);
+    void clear();
+    void push_back(bool bit);
+    void append(Block block);
+
+    template <typename BlockInputIterator>
+    void m_append(BlockInputIterator first, BlockInputIterator last, std::input_iterator_tag)
+    {
+        std::vector<Block, Allocator> v(first, last);
+        m_append(v.begin(), v.end(), std::random_access_iterator_tag());
+    }
+    template <typename BlockInputIterator>
+    void m_append(BlockInputIterator first, BlockInputIterator last, std::forward_iterator_tag)
+    {
+        assert(first != last);
+        block_width_type r = count_extra_bits();
+        std::size_t d = boost::detail::distance(first, last);
+        m_bits.reserve(num_blocks() + d);
+        if (r == 0) {
+            for( ; first != last; ++first)
+                m_bits.push_back(*first); // could use vector<>::insert()
+        }
+        else {
+            m_highest_block() |= (*first << r);
+            do {
+                Block b = *first >> (bits_per_block - r);
+                ++first;
+                m_bits.push_back(b | (first==last? 0 : *first << r));
+            } while (first != last);
+        }
+        m_num_bits += bits_per_block * d;
+    }
+    template <typename BlockInputIterator>
+    void append(BlockInputIterator first, BlockInputIterator last) // strong guarantee
+    {
+        if (first != last) {
+            typename detail::iterator_traits<BlockInputIterator>::iterator_category cat;
+            m_append(first, last, cat);
+        }
+    }
+
+
+    // bitset operations
+    dynamic_bitset& operator&=(const dynamic_bitset& b);
+    dynamic_bitset& operator|=(const dynamic_bitset& b);
+    dynamic_bitset& operator^=(const dynamic_bitset& b);
+    dynamic_bitset& operator-=(const dynamic_bitset& b);
+    dynamic_bitset& operator<<=(size_type n);
+    dynamic_bitset& operator>>=(size_type n);
+    dynamic_bitset operator<<(size_type n) const;
+    dynamic_bitset operator>>(size_type n) const;
+
+    // basic bit operations
+    dynamic_bitset& set(size_type n, bool val = true);
+    dynamic_bitset& set();
+    dynamic_bitset& reset(size_type n);
+    dynamic_bitset& reset();
+    dynamic_bitset& flip(size_type n);
+    dynamic_bitset& flip();
+    bool test(size_type n) const;
+    bool any() const;
+    bool none() const;
+    dynamic_bitset operator~() const;
+    size_type count() const;
+
+    // subscript
+    reference operator[](size_type pos) {
+        return reference(m_bits[block_index(pos)], bit_index(pos));
+    }
+    bool operator[](size_type pos) const { return test(pos); }
+
+    unsigned long to_ulong() const;
+
+    size_type size() const;
+    size_type num_blocks() const;
+    size_type max_size() const;
+    bool empty() const;
+
+    bool is_subset_of(const dynamic_bitset& a) const;
+    bool is_proper_subset_of(const dynamic_bitset& a) const;
+    bool intersects(const dynamic_bitset & a) const;
+
+    // lookup
+    size_type find_first() const;
+    size_type find_next(size_type pos) const;
+
+
+#if !defined BOOST_DYNAMIC_BITSET_DONT_USE_FRIENDS
+    // lexicographical comparison
+    template <typename B, typename A>
+    friend bool operator==(const dynamic_bitset<B, A>& a,
+                           const dynamic_bitset<B, A>& b);
+
+    template <typename B, typename A>
+    friend bool operator<(const dynamic_bitset<B, A>& a,
+                          const dynamic_bitset<B, A>& b);
+
+
+    template <typename B, typename A, typename BlockOutputIterator>
+    friend void to_block_range(const dynamic_bitset<B, A>& b,
+                               BlockOutputIterator result);
+
+    template <typename BlockIterator, typename B, typename A>
+    friend void from_block_range(BlockIterator first, BlockIterator last,
+                                 dynamic_bitset<B, A>& result);
+
+
+    template <typename CharT, typename Traits, typename B, typename A>
+    friend std::basic_istream<CharT, Traits>& operator>>(std::basic_istream<CharT, Traits>& is,
+                                                         dynamic_bitset<B, A>& b);
+
+    template <typename B, typename A, typename stringT>
+    friend void to_string_helper(const dynamic_bitset<B, A> & b, stringT & s, bool dump_all);
+
+
+#endif
+
+
+private:
+    BOOST_STATIC_CONSTANT(block_width_type, ulong_width = std::numeric_limits<unsigned long>::digits);
+    typedef std::vector<block_type, allocator_type> buffer_type;
+
+    void m_zero_unused_bits();
+    bool m_check_invariants() const;
+
+    size_type m_do_find_from(size_type first_block) const;
+
+    block_width_type count_extra_bits() const { return bit_index(size()); }
+    static size_type block_index(size_type pos) { return pos / bits_per_block; }
+    static block_width_type bit_index(size_type pos) { return static_cast<block_width_type>(pos % bits_per_block); }
+    static Block bit_mask(size_type pos) { return Block(1) << bit_index(pos); }
+
+    template <typename CharT, typename Traits, typename Alloc>
+    void init_from_string(const std::basic_string<CharT, Traits, Alloc>& s,
+        typename std::basic_string<CharT, Traits, Alloc>::size_type pos,
+        typename std::basic_string<CharT, Traits, Alloc>::size_type n,
+        size_type num_bits)
+    {
+        assert(pos <= s.size());
+
+        typedef typename std::basic_string<CharT, Traits, Alloc> StrT;
+        typedef typename StrT::traits_type Tr;
+
+        const typename StrT::size_type rlen = (std::min)(n, s.size() - pos);
+        const size_type sz = ( num_bits != npos? num_bits : rlen);
+        m_bits.resize(calc_num_blocks(sz));
+        m_num_bits = sz;
+
+
+        BOOST_DYNAMIC_BITSET_CTYPE_FACET(CharT, fac, std::locale());
+        const CharT one = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '1');
+
+        const size_type m = num_bits < rlen ? num_bits : rlen;
+        typename StrT::size_type i = 0;
+        for( ; i < m; ++i) {
+
+            const CharT c = s[(pos + m - 1) - i];
+
+            assert( Tr::eq(c, one)
+                    || Tr::eq(c, BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '0')) );
+
+            if (Tr::eq(c, one))
+                set(i);
+
+        }
+
+    }
+
+    void init_from_unsigned_long(size_type num_bits,
+                                 unsigned long value/*,
+                                 const Allocator& alloc*/)
+    {
+
+        assert(m_bits.size() == 0);
+
+        m_bits.resize(calc_num_blocks(num_bits));
+        m_num_bits = num_bits;
+
+        typedef unsigned long num_type;
+        typedef boost::detail::dynamic_bitset_impl
+            ::shifter<num_type, bits_per_block, ulong_width> shifter;
+
+        //if (num_bits == 0)
+        //    return;
+
+        // zero out all bits at pos >= num_bits, if any;
+        // note that: num_bits == 0 implies value == 0
+        if (num_bits < static_cast<size_type>(ulong_width)) {
+            const num_type mask = (num_type(1) << num_bits) - 1;
+            value &= mask;
+        }
+
+        typename buffer_type::iterator it = m_bits.begin();
+        for( ; value; shifter::left_shift(value), ++it) {
+            *it = static_cast<block_type>(value);
+        }
+
+    }
+
+
+
+BOOST_DYNAMIC_BITSET_PRIVATE:
+
+    bool m_unchecked_test(size_type pos) const;
+    static size_type calc_num_blocks(size_type num_bits);
+
+    Block&        m_highest_block();
+    const Block&  m_highest_block() const;
+
+    buffer_type m_bits;
+    size_type   m_num_bits;
+
+
+    class bit_appender;
+    friend class bit_appender;
+    class bit_appender {
+      // helper for stream >>
+      // Supplies to the lack of an efficient append at the less
+      // significant end: bits are actually appended "at left" but
+      // rearranged in the destructor. From the perspective of
+      // client code everything works *as if* dynamic_bitset<> had
+      // an append_at_right() function (eventually throwing the same
+      // exceptions as push_back) except that the function is in fact
+      // called bit_appender::do_append().
+      //
+      dynamic_bitset & bs;
+      size_type n;
+      Block mask;
+      Block * current;
+
+      // not implemented
+      bit_appender(const bit_appender &);
+      bit_appender & operator=(const bit_appender &);
+
+    public:
+        bit_appender(dynamic_bitset & r) : bs(r), n(0), mask(0), current(0) {}
+        ~bit_appender() {
+            // reverse the order of blocks, shift
+            // if needed, and then resize
+            //
+            std::reverse(bs.m_bits.begin(), bs.m_bits.end());
+            const block_width_type offs = bit_index(n);
+            if (offs)
+                bs >>= (bits_per_block - offs);
+            bs.resize(n); // doesn't enlarge, so can't throw
+            assert(bs.m_check_invariants());
+        }
+        inline void do_append(bool value) {
+
+            if (mask == 0) {
+                bs.append(Block(0));
+                current = &bs.m_highest_block();
+                mask = Block(1) << (bits_per_block - 1);
+            }
+
+            if(value)
+                *current |= mask;
+
+            mask /= 2;
+            ++n;
+        }
+        size_type get_count() const { return n; }
+    };
+
+};
+
+#if !defined BOOST_NO_INCLASS_MEMBER_INITIALIZATION
+
+template <typename Block, typename Allocator>
+const typename dynamic_bitset<Block, Allocator>::block_width_type
+dynamic_bitset<Block, Allocator>::bits_per_block;
+
+template <typename Block, typename Allocator>
+const typename dynamic_bitset<Block, Allocator>::size_type
+dynamic_bitset<Block, Allocator>::npos;
+
+template <typename Block, typename Allocator>
+const typename dynamic_bitset<Block, Allocator>::block_width_type
+dynamic_bitset<Block, Allocator>::ulong_width;
+
+#endif
+
+// Global Functions:
+
+// comparison
+template <typename Block, typename Allocator>
+bool operator!=(const dynamic_bitset<Block, Allocator>& a,
+                const dynamic_bitset<Block, Allocator>& b);
+
+template <typename Block, typename Allocator>
+bool operator<=(const dynamic_bitset<Block, Allocator>& a,
+                const dynamic_bitset<Block, Allocator>& b);
+
+template <typename Block, typename Allocator>
+bool operator>(const dynamic_bitset<Block, Allocator>& a,
+               const dynamic_bitset<Block, Allocator>& b);
+
+template <typename Block, typename Allocator>
+bool operator>=(const dynamic_bitset<Block, Allocator>& a,
+                const dynamic_bitset<Block, Allocator>& b);
+
+// stream operators
+#ifdef BOOST_OLD_IOSTREAMS
+template <typename Block, typename Allocator>
+std::ostream& operator<<(std::ostream& os,
+                         const dynamic_bitset<Block, Allocator>& b);
+
+template <typename Block, typename Allocator>
+std::istream& operator>>(std::istream& is, dynamic_bitset<Block,Allocator>& b);
+#else
+template <typename CharT, typename Traits, typename Block, typename Allocator>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os,
+           const dynamic_bitset<Block, Allocator>& b);
+
+template <typename CharT, typename Traits, typename Block, typename Allocator>
+std::basic_istream<CharT, Traits>&
+operator>>(std::basic_istream<CharT, Traits>& is,
+           dynamic_bitset<Block, Allocator>& b);
+#endif
+
+// bitset operations
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+operator&(const dynamic_bitset<Block, Allocator>& b1,
+          const dynamic_bitset<Block, Allocator>& b2);
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+operator|(const dynamic_bitset<Block, Allocator>& b1,
+          const dynamic_bitset<Block, Allocator>& b2);
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+operator^(const dynamic_bitset<Block, Allocator>& b1,
+          const dynamic_bitset<Block, Allocator>& b2);
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+operator-(const dynamic_bitset<Block, Allocator>& b1,
+          const dynamic_bitset<Block, Allocator>& b2);
+
+// namespace scope swap
+template<typename Block, typename Allocator>
+void swap(dynamic_bitset<Block, Allocator>& b1,
+          dynamic_bitset<Block, Allocator>& b2);
+
+
+template <typename Block, typename Allocator, typename stringT>
+void
+to_string(const dynamic_bitset<Block, Allocator>& b, stringT & s);
+
+template <typename Block, typename Allocator, typename BlockOutputIterator>
+void
+to_block_range(const dynamic_bitset<Block, Allocator>& b,
+               BlockOutputIterator result);
+
+
+template <typename BlockIterator, typename B, typename A>
+inline void
+from_block_range(BlockIterator first, BlockIterator last,
+                 dynamic_bitset<B, A>& result)
+{
+    // PRE: distance(first, last) <= numblocks()
+    std::copy (first, last, result.m_bits.begin());
+}
+
+//=============================================================================
+// dynamic_bitset implementation
+
+
+//-----------------------------------------------------------------------------
+// constructors, etc.
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>::dynamic_bitset(const Allocator& alloc)
+  : m_bits(alloc), m_num_bits(0)
+{
+
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>::
+dynamic_bitset(size_type num_bits, unsigned long value, const Allocator& alloc)
+    : m_bits(alloc),
+      m_num_bits(0)
+{
+    init_from_unsigned_long(num_bits, value);
+}
+
+// copy constructor
+template <typename Block, typename Allocator>
+inline dynamic_bitset<Block, Allocator>::
+dynamic_bitset(const dynamic_bitset& b)
+  : m_bits(b.m_bits), m_num_bits(b.m_num_bits)
+{
+
+}
+
+template <typename Block, typename Allocator>
+inline dynamic_bitset<Block, Allocator>::
+~dynamic_bitset()
+{
+    assert(m_check_invariants());
+}
+
+template <typename Block, typename Allocator>
+inline void dynamic_bitset<Block, Allocator>::
+swap(dynamic_bitset<Block, Allocator>& b) // no throw
+{
+    std::swap(m_bits, b.m_bits);
+    std::swap(m_num_bits, b.m_num_bits);
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>& dynamic_bitset<Block, Allocator>::
+operator=(const dynamic_bitset<Block, Allocator>& b)
+{
+    m_bits = b.m_bits;
+    m_num_bits = b.m_num_bits;
+    return *this;
+}
+
+template <typename Block, typename Allocator>
+inline typename dynamic_bitset<Block, Allocator>::allocator_type
+dynamic_bitset<Block, Allocator>::get_allocator() const
+{
+    return m_bits.get_allocator();
+}
+
+//-----------------------------------------------------------------------------
+// size changing operations
+
+template <typename Block, typename Allocator>
+void dynamic_bitset<Block, Allocator>::
+resize(size_type num_bits, bool value) // strong guarantee
+{
+
+  const size_type old_num_blocks = num_blocks();
+  const size_type required_blocks = calc_num_blocks(num_bits);
+
+  const block_type v = value? ~Block(0) : Block(0);
+
+  if (required_blocks != old_num_blocks) {
+    m_bits.resize(required_blocks, v); // s.g. (copy)
+  }
+
+
+  // At this point:
+  //
+  //  - if the buffer was shrunk, we have nothing more to do,
+  //    except a call to m_zero_unused_bits()
+  //
+  //  - if it was enlarged, all the (used) bits in the new blocks have
+  //    the correct value, but we have not yet touched those bits, if
+  //    any, that were 'unused bits' before enlarging: if value == true,
+  //    they must be set.
+
+  if (value && (num_bits > m_num_bits)) {
+
+    const block_width_type extra_bits = count_extra_bits();
+    if (extra_bits) {
+        assert(old_num_blocks >= 1 && old_num_blocks <= m_bits.size());
+
+        // Set them.
+        m_bits[old_num_blocks - 1] |= (v << extra_bits);
+    }
+
+  }
+
+  m_num_bits = num_bits;
+  m_zero_unused_bits();
+
+}
+
+template <typename Block, typename Allocator>
+void dynamic_bitset<Block, Allocator>::
+clear() // no throw
+{
+  m_bits.clear();
+  m_num_bits = 0;
+}
+
+
+template <typename Block, typename Allocator>
+void dynamic_bitset<Block, Allocator>::
+push_back(bool bit)
+{
+  const size_type sz = size();
+  resize(sz + 1);
+  set(sz, bit);
+}
+
+template <typename Block, typename Allocator>
+void dynamic_bitset<Block, Allocator>::
+append(Block value) // strong guarantee
+{
+    const block_width_type r = count_extra_bits();
+
+    if (r == 0) {
+        // the buffer is empty, or all blocks are filled
+        m_bits.push_back(value);
+    }
+    else {
+        m_bits.push_back(value >> (bits_per_block - r));
+        m_bits[m_bits.size() - 2] |= (value << r); // m_bits.size() >= 2
+    }
+
+    m_num_bits += bits_per_block;
+    assert(m_check_invariants());
+
+}
+
+
+//-----------------------------------------------------------------------------
+// bitset operations
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::operator&=(const dynamic_bitset& rhs)
+{
+    assert(size() == rhs.size());
+    for (size_type i = 0; i < num_blocks(); ++i)
+        m_bits[i] &= rhs.m_bits[i];
+    return *this;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::operator|=(const dynamic_bitset& rhs)
+{
+    assert(size() == rhs.size());
+    for (size_type i = 0; i < num_blocks(); ++i)
+        m_bits[i] |= rhs.m_bits[i];
+    //m_zero_unused_bits();
+    return *this;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::operator^=(const dynamic_bitset& rhs)
+{
+    assert(size() == rhs.size());
+    for (size_type i = 0; i < this->num_blocks(); ++i)
+        m_bits[i] ^= rhs.m_bits[i];
+    //m_zero_unused_bits();
+    return *this;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::operator-=(const dynamic_bitset& rhs)
+{
+    assert(size() == rhs.size());
+    for (size_type i = 0; i < num_blocks(); ++i)
+        m_bits[i] &= ~rhs.m_bits[i];
+    //m_zero_unused_bits();
+    return *this;
+}
+
+//
+// NOTE:
+//  Note that the 'if (r != 0)' is crucial to avoid undefined
+//  behavior when the left hand operand of >> isn't promoted to a
+//  wider type (because rs would be too large).
+//
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::operator<<=(size_type n)
+{
+    if (n >= m_num_bits)
+        return reset();
+    //else
+    if (n > 0) {
+
+        size_type    const last = num_blocks() - 1;  // num_blocks() is >= 1
+        size_type    const div  = n / bits_per_block; // div is <= last
+        block_width_type const r = bit_index(n);
+        block_type * const b    = &m_bits[0];
+
+        if (r != 0) {
+
+            block_width_type const rs = bits_per_block - r;
+
+            for (size_type i = last-div; i>0; --i) {
+                b[i+div] = (b[i] << r) | (b[i-1] >> rs);
+            }
+            b[div] = b[0] << r;
+
+        }
+        else {
+            for (size_type i = last-div; i>0; --i) {
+                b[i+div] = b[i];
+            }
+            b[div] = b[0];
+        }
+
+        // zero out div blocks at the less significant end
+        std::fill_n(b, div, static_cast<block_type>(0));
+
+        // zero out any 1 bit that flowed into the unused part
+        m_zero_unused_bits(); // thanks to Lester Gong
+
+    }
+
+    return *this;
+
+
+}
+
+
+//
+// NOTE:
+//  see the comments to operator <<=
+//
+template <typename B, typename A>
+dynamic_bitset<B, A> & dynamic_bitset<B, A>::operator>>=(size_type n) {
+    if (n >= m_num_bits) {
+        return reset();
+    }
+    //else
+    if (n>0) {
+
+        size_type  const last  = num_blocks() - 1; // num_blocks() is >= 1
+        size_type  const div   = n / bits_per_block;   // div is <= last
+        block_width_type const r     = bit_index(n);
+        block_type * const b   = &m_bits[0];
+
+
+        if (r != 0) {
+
+            block_width_type const ls = bits_per_block - r;
+
+            for (size_type i = div; i < last; ++i) {
+                b[i-div] = (b[i] >> r) | (b[i+1]  << ls);
+            }
+            // r bits go to zero
+            b[last-div] = b[last] >> r;
+        }
+
+        else {
+            for (size_type i = div; i <= last; ++i) {
+                b[i-div] = b[i];
+            }
+            // note the '<=': the last iteration 'absorbs'
+            // b[last-div] = b[last] >> 0;
+        }
+
+
+
+        // div blocks are zero filled at the most significant end
+        std::fill_n(b + (num_blocks()-div), div, static_cast<block_type>(0));
+    }
+
+    return *this;
+}
+
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+dynamic_bitset<Block, Allocator>::operator<<(size_type n) const
+{
+    dynamic_bitset r(*this);
+    return r <<= n;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+dynamic_bitset<Block, Allocator>::operator>>(size_type n) const
+{
+    dynamic_bitset r(*this);
+    return r >>= n;
+}
+
+
+//-----------------------------------------------------------------------------
+// basic bit operations
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::set(size_type pos, bool val)
+{
+    assert(pos < m_num_bits);
+
+    if (val)
+        m_bits[block_index(pos)] |= bit_mask(pos);
+    else
+        reset(pos);
+
+    return *this;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::set()
+{
+  std::fill(m_bits.begin(), m_bits.end(), ~Block(0));
+  m_zero_unused_bits();
+  return *this;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::reset(size_type pos)
+{
+    assert(pos < m_num_bits);
+#if defined __MWERKS__ && BOOST_WORKAROUND(__MWERKS__, <= 0x3003) // 8.x
+    // CodeWarrior 8 generates incorrect code when the &=~ is compiled,
+    // use the |^ variation instead.. <grafik>
+    m_bits[block_index(pos)] |= bit_mask(pos);
+    m_bits[block_index(pos)] ^= bit_mask(pos);
+#else
+    m_bits[block_index(pos)] &= ~bit_mask(pos);
+#endif
+    return *this;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::reset()
+{
+  std::fill(m_bits.begin(), m_bits.end(), Block(0));
+  return *this;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::flip(size_type pos)
+{
+    assert(pos < m_num_bits);
+    m_bits[block_index(pos)] ^= bit_mask(pos);
+    return *this;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>&
+dynamic_bitset<Block, Allocator>::flip()
+{
+    for (size_type i = 0; i < num_blocks(); ++i)
+        m_bits[i] = ~m_bits[i];
+    m_zero_unused_bits();
+    return *this;
+}
+
+template <typename Block, typename Allocator>
+bool dynamic_bitset<Block, Allocator>::m_unchecked_test(size_type pos) const
+{
+    return (m_bits[block_index(pos)] & bit_mask(pos)) != 0;
+}
+
+template <typename Block, typename Allocator>
+bool dynamic_bitset<Block, Allocator>::test(size_type pos) const
+{
+    assert(pos < m_num_bits);
+    return m_unchecked_test(pos);
+}
+
+template <typename Block, typename Allocator>
+bool dynamic_bitset<Block, Allocator>::any() const
+{
+    for (size_type i = 0; i < num_blocks(); ++i)
+        if (m_bits[i])
+            return true;
+    return false;
+}
+
+template <typename Block, typename Allocator>
+inline bool dynamic_bitset<Block, Allocator>::none() const
+{
+    return !any();
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+dynamic_bitset<Block, Allocator>::operator~() const
+{
+    dynamic_bitset b(*this);
+    b.flip();
+    return b;
+}
+
+template <typename Block, typename Allocator>
+typename dynamic_bitset<Block, Allocator>::size_type
+dynamic_bitset<Block, Allocator>::count() const
+{
+    using detail::dynamic_bitset_impl::table_width;
+    using detail::dynamic_bitset_impl::access_by_bytes;
+    using detail::dynamic_bitset_impl::access_by_blocks;
+    using detail::dynamic_bitset_impl::value_to_type;
+
+#if BOOST_WORKAROUND(__GNUC__, == 4) && (__GNUC_MINOR__ == 3) && (__GNUC_PATCHLEVEL__ == 3)
+    // NOTE: Explicit qualification of "bits_per_block"
+    //       breaks compilation on gcc 4.3.3
+    enum { no_padding = bits_per_block == CHAR_BIT * sizeof(Block) };
+#else
+    // NOTE: Explicitly qualifying "bits_per_block" to workaround
+    //       regressions of gcc 3.4.x
+    enum { no_padding =
+        dynamic_bitset<Block, Allocator>::bits_per_block
+        == CHAR_BIT * sizeof(Block) };
+#endif
+
+    enum { enough_table_width = table_width >= CHAR_BIT };
+
+    enum { mode = (no_padding && enough_table_width)
+                          ? access_by_bytes
+                          : access_by_blocks };
+
+    return do_count(m_bits.begin(), num_blocks(), Block(0),
+                    static_cast<value_to_type<(bool)mode> *>(0));
+}
+
+
+//-----------------------------------------------------------------------------
+// conversions
+
+
+template <typename B, typename A, typename stringT>
+void to_string_helper(const dynamic_bitset<B, A> & b, stringT & s,
+                      bool dump_all)
+{
+    typedef typename stringT::traits_type Tr;
+    typedef typename stringT::value_type  Ch;
+
+    BOOST_DYNAMIC_BITSET_CTYPE_FACET(Ch, fac, std::locale());
+    const Ch zero = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '0');
+    const Ch one  = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '1');
+
+    // Note that this function may access (when
+    // dump_all == true) bits beyond position size() - 1
+
+    typedef typename dynamic_bitset<B, A>::size_type size_type;
+
+    const size_type len = dump_all?
+         dynamic_bitset<B, A>::bits_per_block * b.num_blocks():
+         b.size();
+    s.assign (len, zero);
+
+    for (size_type i = 0; i < len; ++i) {
+        if (b.m_unchecked_test(i))
+            Tr::assign(s[len - 1 - i], one);
+
+    }
+
+}
+
+
+// A comment similar to the one about the constructor from
+// basic_string can be done here. Thanks to James Kanze for
+// making me (Gennaro) realize this important separation of
+// concerns issue, as well as many things about i18n.
+//
+template <typename Block, typename Allocator, typename stringT>
+inline void
+to_string(const dynamic_bitset<Block, Allocator>& b, stringT& s)
+{
+    to_string_helper(b, s, false);
+}
+
+
+// Differently from to_string this function dumps out
+// every bit of the internal representation (may be
+// useful for debugging purposes)
+//
+template <typename B, typename A, typename stringT>
+inline void
+dump_to_string(const dynamic_bitset<B, A>& b, stringT& s)
+{
+    to_string_helper(b, s, true /* =dump_all*/);
+}
+
+template <typename Block, typename Allocator, typename BlockOutputIterator>
+inline void
+to_block_range(const dynamic_bitset<Block, Allocator>& b,
+               BlockOutputIterator result)
+{
+    // note how this copies *all* bits, including the
+    // unused ones in the last block (which are zero)
+    std::copy(b.m_bits.begin(), b.m_bits.end(), result);
+}
+
+template <typename Block, typename Allocator>
+unsigned long dynamic_bitset<Block, Allocator>::
+to_ulong() const
+{
+
+  if (m_num_bits == 0)
+      return 0; // convention
+
+  // Check for overflows. This may be a performance burden on very
+  // large bitsets but is required by the specification, sorry
+  if (find_next(ulong_width - 1) != npos)
+    throw std::overflow_error("boost::dynamic_bitset::to_ulong overflow");
+
+
+  // Ok, from now on we can be sure there's no "on" bit
+  // beyond the "allowed" positions
+  typedef unsigned long result_type;
+
+  const size_type maximum_size =
+            (std::min)(m_num_bits, static_cast<size_type>(ulong_width));
+
+  const size_type last_block = block_index( maximum_size - 1 );
+
+  assert((last_block * bits_per_block) < static_cast<size_type>(ulong_width));
+
+  result_type result = 0;
+  for (size_type i = 0; i <= last_block; ++i) {
+    const size_type offset = i * bits_per_block;
+    result |= (static_cast<result_type>(m_bits[i]) << offset);
+  }
+
+  return result;
+}
+
+template <typename Block, typename Allocator>
+inline typename dynamic_bitset<Block, Allocator>::size_type
+dynamic_bitset<Block, Allocator>::size() const
+{
+    return m_num_bits;
+}
+
+template <typename Block, typename Allocator>
+inline typename dynamic_bitset<Block, Allocator>::size_type
+dynamic_bitset<Block, Allocator>::num_blocks() const
+{
+    return m_bits.size();
+}
+
+template <typename Block, typename Allocator>
+inline typename dynamic_bitset<Block, Allocator>::size_type
+dynamic_bitset<Block, Allocator>::max_size() const
+{
+    // Semantics of vector<>::max_size() aren't very clear
+    // (see lib issue 197) and many library implementations
+    // simply return dummy values, _unrelated_ to the underlying
+    // allocator.
+    //
+    // Given these problems, I was tempted to not provide this
+    // function at all but the user could need it if he provides
+    // his own allocator.
+    //
+
+    const size_type m = detail::dynamic_bitset_impl::
+                        vector_max_size_workaround(m_bits);
+
+    return m <= (size_type(-1)/bits_per_block) ?
+        m * bits_per_block :
+        size_type(-1);
+}
+
+template <typename Block, typename Allocator>
+inline bool dynamic_bitset<Block, Allocator>::empty() const
+{
+  return size() == 0;
+}
+
+template <typename Block, typename Allocator>
+bool dynamic_bitset<Block, Allocator>::
+is_subset_of(const dynamic_bitset<Block, Allocator>& a) const
+{
+    assert(size() == a.size());
+    for (size_type i = 0; i < num_blocks(); ++i)
+        if (m_bits[i] & ~a.m_bits[i])
+            return false;
+    return true;
+}
+
+template <typename Block, typename Allocator>
+bool dynamic_bitset<Block, Allocator>::
+is_proper_subset_of(const dynamic_bitset<Block, Allocator>& a) const
+{
+    assert(size() == a.size());
+    assert(num_blocks() == a.num_blocks());
+
+    bool proper = false;
+    for (size_type i = 0; i < num_blocks(); ++i) {
+        const Block & bt =   m_bits[i];
+        const Block & ba = a.m_bits[i];
+
+        if (bt & ~ba)
+            return false; // not a subset at all
+        if (ba & ~bt)
+            proper = true;
+    }
+    return proper;
+}
+
+template <typename Block, typename Allocator>
+bool dynamic_bitset<Block, Allocator>::intersects(const dynamic_bitset & b) const
+{
+    size_type common_blocks = num_blocks() < b.num_blocks()
+                              ? num_blocks() : b.num_blocks();
+
+    for(size_type i = 0; i < common_blocks; ++i) {
+        if(m_bits[i] & b.m_bits[i])
+            return true;
+    }
+    return false;
+}
+
+// --------------------------------
+// lookup
+
+
+// look for the first bit "on", starting
+// from the block with index first_block
+//
+template <typename Block, typename Allocator>
+typename dynamic_bitset<Block, Allocator>::size_type
+dynamic_bitset<Block, Allocator>::m_do_find_from(size_type first_block) const
+{
+    size_type i = first_block;
+
+    // skip null blocks
+    while (i < num_blocks() && m_bits[i] == 0)
+        ++i;
+
+    if (i >= num_blocks())
+        return npos; // not found
+
+    return i * bits_per_block + boost::lowest_bit(m_bits[i]);
+
+}
+
+
+template <typename Block, typename Allocator>
+typename dynamic_bitset<Block, Allocator>::size_type
+dynamic_bitset<Block, Allocator>::find_first() const
+{
+    return m_do_find_from(0);
+}
+
+
+template <typename Block, typename Allocator>
+typename dynamic_bitset<Block, Allocator>::size_type
+dynamic_bitset<Block, Allocator>::find_next(size_type pos) const
+{
+
+    const size_type sz = size();
+    if (pos >= (sz-1) || sz == 0)
+        return npos;
+
+    ++pos;
+
+    const size_type blk = block_index(pos);
+    const block_width_type ind = bit_index(pos);
+
+    // mask out bits before pos
+    const Block fore = m_bits[blk] & ( ~Block(0) << ind );
+
+    return fore?
+        blk * bits_per_block + lowest_bit(fore)
+        :
+        m_do_find_from(blk + 1);
+
+}
+
+
+
+//-----------------------------------------------------------------------------
+// comparison
+
+template <typename Block, typename Allocator>
+bool operator==(const dynamic_bitset<Block, Allocator>& a,
+                const dynamic_bitset<Block, Allocator>& b)
+{
+    return (a.m_num_bits == b.m_num_bits)
+           && (a.m_bits == b.m_bits);
+}
+
+template <typename Block, typename Allocator>
+inline bool operator!=(const dynamic_bitset<Block, Allocator>& a,
+                       const dynamic_bitset<Block, Allocator>& b)
+{
+    return !(a == b);
+}
+
+template <typename Block, typename Allocator>
+bool operator<(const dynamic_bitset<Block, Allocator>& a,
+               const dynamic_bitset<Block, Allocator>& b)
+{
+    assert(a.size() == b.size());
+    typedef typename dynamic_bitset<Block, Allocator>::size_type size_type;
+
+    //if (a.size() == 0)
+    //  return false;
+
+    // Since we are storing the most significant bit
+    // at pos == size() - 1, we need to do the comparisons in reverse.
+    //
+    for (size_type ii = a.num_blocks(); ii > 0; --ii) {
+      size_type i = ii-1;
+      if (a.m_bits[i] < b.m_bits[i])
+        return true;
+      else if (a.m_bits[i] > b.m_bits[i])
+        return false;
+    }
+    return false;
+}
+
+template <typename Block, typename Allocator>
+inline bool operator<=(const dynamic_bitset<Block, Allocator>& a,
+                       const dynamic_bitset<Block, Allocator>& b)
+{
+    return !(a > b);
+}
+
+template <typename Block, typename Allocator>
+inline bool operator>(const dynamic_bitset<Block, Allocator>& a,
+                      const dynamic_bitset<Block, Allocator>& b)
+{
+    return b < a;
+}
+
+template <typename Block, typename Allocator>
+inline bool operator>=(const dynamic_bitset<Block, Allocator>& a,
+                       const dynamic_bitset<Block, Allocator>& b)
+{
+    return !(a < b);
+}
+
+//-----------------------------------------------------------------------------
+// stream operations
+
+#ifdef BOOST_OLD_IOSTREAMS
+template < typename Block, typename Alloc>
+std::ostream&
+operator<<(std::ostream& os, const dynamic_bitset<Block, Alloc>& b)
+{
+    // NOTE: since this is aimed at "classic" iostreams, exception
+    // masks on the stream are not supported. The library that
+    // ships with gcc 2.95 has an exceptions() member function but
+    // nothing is actually implemented; not even the class ios::failure.
+
+    using namespace std;
+
+    const ios::iostate ok = ios::goodbit;
+    ios::iostate err = ok;
+
+    if (os.opfx()) {
+
+        //try
+        typedef typename dynamic_bitset<Block, Alloc>::size_type bitsetsize_type;
+
+        const bitsetsize_type sz = b.size();
+        std::streambuf * buf = os.rdbuf();
+        size_t npad = os.width() <= 0  // careful: os.width() is signed (and can be < 0)
+            || (bitsetsize_type) os.width() <= sz? 0 : os.width() - sz;
+
+        const char fill_char = os.fill();
+        const ios::fmtflags adjustfield = os.flags() & ios::adjustfield;
+
+        // if needed fill at left; pad is decresed along the way
+        if (adjustfield != ios::left) {
+            for (; 0 < npad; --npad)
+                if (fill_char != buf->sputc(fill_char)) {
+                    err |= ios::failbit;
+                    break;
+                }
+        }
+
+        if (err == ok) {
+            // output the bitset
+            for (bitsetsize_type i = b.size(); 0 < i; --i) {
+                const char dig = b.test(i-1)? '1' : '0';
+                if (EOF == buf->sputc(dig)) {
+                    err |= ios::failbit;
+                    break;
+                }
+            }
+        }
+
+        if (err == ok) {
+            // if needed fill at right
+            for (; 0 < npad; --npad) {
+                if (fill_char != buf->sputc(fill_char)) {
+                    err |= ios::failbit;
+                    break;
+                }
+            }
+        }
+
+        os.osfx();
+        os.width(0);
+
+    } // if opfx
+
+    if(err != ok)
+        os.setstate(err); // assume this does NOT throw
+    return os;
+
+}
+#else
+
+template <typename Ch, typename Tr, typename Block, typename Alloc>
+std::basic_ostream<Ch, Tr>&
+operator<<(std::basic_ostream<Ch, Tr>& os,
+           const dynamic_bitset<Block, Alloc>& b)
+{
+
+    using namespace std;
+
+    const ios_base::iostate ok = ios_base::goodbit;
+    ios_base::iostate err = ok;
+
+    typename basic_ostream<Ch, Tr>::sentry cerberos(os);
+    if (cerberos) {
+
+        BOOST_DYNAMIC_BITSET_CTYPE_FACET(Ch, fac, os.getloc());
+        const Ch zero = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '0');
+        const Ch one  = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '1');
+
+        try {
+
+            typedef typename dynamic_bitset<Block, Alloc>::size_type bitsetsize_type;
+            typedef basic_streambuf<Ch, Tr> buffer_type;
+
+            buffer_type * buf = os.rdbuf();
+            size_t npad = os.width() <= 0  // careful: os.width() is signed (and can be < 0)
+                || (bitsetsize_type) os.width() <= b.size()? 0 : os.width() - b.size();
+
+            const Ch fill_char = os.fill();
+            const ios_base::fmtflags adjustfield = os.flags() & ios_base::adjustfield;
+
+            // if needed fill at left; pad is decresed along the way
+            if (adjustfield != ios_base::left) {
+                for (; 0 < npad; --npad)
+                    if (Tr::eq_int_type(Tr::eof(), buf->sputc(fill_char))) {
+                          err |= ios_base::failbit;
+                          break;
+                    }
+            }
+
+            if (err == ok) {
+                // output the bitset
+                for (bitsetsize_type i = b.size(); 0 < i; --i) {
+                    typename buffer_type::int_type
+                        ret = buf->sputc(b.test(i-1)? one : zero);
+                    if (Tr::eq_int_type(Tr::eof(), ret)) {
+                        err |= ios_base::failbit;
+                        break;
+                    }
+                }
+            }
+
+            if (err == ok) {
+                // if needed fill at right
+                for (; 0 < npad; --npad) {
+                    if (Tr::eq_int_type(Tr::eof(), buf->sputc(fill_char))) {
+                        err |= ios_base::failbit;
+                        break;
+                    }
+                }
+            }
+
+
+            os.width(0);
+
+        } catch (...) { // see std 27.6.1.1/4
+            bool rethrow = false;
+            try { os.setstate(ios_base::failbit); } catch (...) { rethrow = true; }
+
+            if (rethrow)
+                throw;
+        }
+    }
+
+    if(err != ok)
+        os.setstate(err); // may throw exception
+    return os;
+
+}
+#endif
+
+
+#ifdef BOOST_OLD_IOSTREAMS
+
+    // A sentry-like class that calls isfx in its destructor.
+    // "Necessary" because bit_appender::do_append may throw.
+    class pseudo_sentry {
+        std::istream & m_r;
+        const bool m_ok;
+    public:
+        explicit pseudo_sentry(std::istream & r) : m_r(r), m_ok(r.ipfx(0)) { }
+        ~pseudo_sentry() { m_r.isfx(); }
+        operator bool() const { return m_ok; }
+    };
+
+template <typename Block, typename Alloc>
+std::istream&
+operator>>(std::istream& is, dynamic_bitset<Block, Alloc>& b)
+{
+
+// Extractor for classic IO streams (libstdc++ < 3.0)
+// ----------------------------------------------------//
+//  It's assumed that the stream buffer functions, and
+//  the stream's setstate() _cannot_ throw.
+
+
+    typedef dynamic_bitset<Block, Alloc> bitset_type;
+    typedef typename bitset_type::size_type size_type;
+
+    std::ios::iostate err = std::ios::goodbit;
+    pseudo_sentry cerberos(is); // skips whitespaces
+    if(cerberos) {
+
+        b.clear();
+
+        const std::streamsize w = is.width();
+        const size_type limit = w > 0 && static_cast<size_type>(w) < b.max_size()
+                                                         ? w : b.max_size();
+        typename bitset_type::bit_appender appender(b);
+        std::streambuf * buf = is.rdbuf();
+        for(int c = buf->sgetc(); appender.get_count() < limit; c = buf->snextc() ) {
+
+            if (c == EOF) {
+                err |= std::ios::eofbit;
+                break;
+            }
+            else if (char(c) != '0' && char(c) != '1')
+                break; // non digit character
+
+            else {
+                try {
+                    appender.do_append(char(c) == '1');
+                }
+                catch(...) {
+                    is.setstate(std::ios::failbit); // assume this can't throw
+                    throw;
+                }
+            }
+
+        } // for
+    }
+
+    is.width(0);
+    if (b.size() == 0)
+        err |= std::ios::failbit;
+    if (err != std::ios::goodbit)
+        is.setstate (err); // may throw
+
+    return is;
+}
+
+#else // BOOST_OLD_IOSTREAMS
+
+template <typename Ch, typename Tr, typename Block, typename Alloc>
+std::basic_istream<Ch, Tr>&
+operator>>(std::basic_istream<Ch, Tr>& is, dynamic_bitset<Block, Alloc>& b)
+{
+
+    using namespace std;
+
+    typedef dynamic_bitset<Block, Alloc> bitset_type;
+    typedef typename bitset_type::size_type size_type;
+
+    const streamsize w = is.width();
+    const size_type limit = 0 < w && static_cast<size_type>(w) < b.max_size()?
+                                         w : b.max_size();
+
+    ios_base::iostate err = ios_base::goodbit;
+    typename basic_istream<Ch, Tr>::sentry cerberos(is); // skips whitespaces
+    if(cerberos) {
+
+        // in accordance with prop. resol. of lib DR 303 [last checked 4 Feb 2004]
+        BOOST_DYNAMIC_BITSET_CTYPE_FACET(Ch, fac, is.getloc());
+        const Ch zero = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '0');
+        const Ch one  = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '1');
+
+        b.clear();
+        try {
+            typename bitset_type::bit_appender appender(b);
+            basic_streambuf <Ch, Tr> * buf = is.rdbuf();
+            typename Tr::int_type c = buf->sgetc();
+            for( ; appender.get_count() < limit; c = buf->snextc() ) {
+
+                if (Tr::eq_int_type(Tr::eof(), c)) {
+                    err |= ios_base::eofbit;
+                    break;
+                }
+                else {
+                    const Ch to_c = Tr::to_char_type(c);
+                    const bool is_one = Tr::eq(to_c, one);
+
+                    if (!is_one && !Tr::eq(to_c, zero))
+                        break; // non digit character
+
+                    appender.do_append(is_one);
+
+                }
+
+            } // for
+        }
+        catch (...) {
+            // catches from stream buf, or from vector:
+            //
+            // bits_stored bits have been extracted and stored, and
+            // either no further character is extractable or we can't
+            // append to the underlying vector (out of memory)
+
+            bool rethrow = false;   // see std 27.6.1.1/4
+            try { is.setstate(ios_base::badbit); }
+            catch(...) { rethrow = true; }
+
+            if (rethrow)
+                throw;
+
+        }
+    }
+
+    is.width(0);
+    if (b.size() == 0 /*|| !cerberos*/)
+        err |= ios_base::failbit;
+    if (err != ios_base::goodbit)
+        is.setstate (err); // may throw
+
+    return is;
+
+}
+
+
+#endif
+
+
+//-----------------------------------------------------------------------------
+// bitset operations
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+operator&(const dynamic_bitset<Block, Allocator>& x,
+          const dynamic_bitset<Block, Allocator>& y)
+{
+    dynamic_bitset<Block, Allocator> b(x);
+    return b &= y;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+operator|(const dynamic_bitset<Block, Allocator>& x,
+          const dynamic_bitset<Block, Allocator>& y)
+{
+    dynamic_bitset<Block, Allocator> b(x);
+    return b |= y;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+operator^(const dynamic_bitset<Block, Allocator>& x,
+          const dynamic_bitset<Block, Allocator>& y)
+{
+    dynamic_bitset<Block, Allocator> b(x);
+    return b ^= y;
+}
+
+template <typename Block, typename Allocator>
+dynamic_bitset<Block, Allocator>
+operator-(const dynamic_bitset<Block, Allocator>& x,
+          const dynamic_bitset<Block, Allocator>& y)
+{
+    dynamic_bitset<Block, Allocator> b(x);
+    return b -= y;
+}
+
+//-----------------------------------------------------------------------------
+// namespace scope swap
+
+template<typename Block, typename Allocator>
+inline void
+swap(dynamic_bitset<Block, Allocator>& left,
+     dynamic_bitset<Block, Allocator>& right) // no throw
+{
+    left.swap(right);
+}
+
+
+//-----------------------------------------------------------------------------
+// private (on conforming compilers) member functions
+
+
+template <typename Block, typename Allocator>
+inline typename dynamic_bitset<Block, Allocator>::size_type
+dynamic_bitset<Block, Allocator>::calc_num_blocks(size_type num_bits)
+{
+    return num_bits / bits_per_block
+           + static_cast<int>( num_bits % bits_per_block != 0 );
+}
+
+// gives a reference to the highest block
+//
+template <typename Block, typename Allocator>
+inline Block& dynamic_bitset<Block, Allocator>::m_highest_block()
+{
+    return const_cast<Block &>
+           (static_cast<const dynamic_bitset *>(this)->m_highest_block());
+}
+
+// gives a const-reference to the highest block
+//
+template <typename Block, typename Allocator>
+inline const Block& dynamic_bitset<Block, Allocator>::m_highest_block() const
+{
+    assert(size() > 0 && num_blocks() > 0);
+    return m_bits.back();
+}
+
+
+// If size() is not a multiple of bits_per_block
+// then not all the bits in the last block are used.
+// This function resets the unused bits (convenient
+// for the implementation of many member functions)
+//
+template <typename Block, typename Allocator>
+inline void dynamic_bitset<Block, Allocator>::m_zero_unused_bits()
+{
+    assert (num_blocks() == calc_num_blocks(m_num_bits));
+
+    // if != 0 this is the number of bits used in the last block
+    const block_width_type extra_bits = count_extra_bits();
+
+    if (extra_bits != 0)
+        m_highest_block() &= ~(~static_cast<Block>(0) << extra_bits);
+
+}
+
+// check class invariants
+template <typename Block, typename Allocator>
+bool dynamic_bitset<Block, Allocator>::m_check_invariants() const
+{
+    const block_width_type extra_bits = count_extra_bits();
+    if (extra_bits > 0) {
+        block_type const mask = (~static_cast<Block>(0) << extra_bits);
+        if ((m_highest_block() & mask) != 0)
+            return false;
+    }
+    if (m_bits.size() > m_bits.capacity() || num_blocks() != calc_num_blocks(size()))
+        return false;
+
+    return true;
+
+}
+
+
+} // namespace boost
+
+
+#undef BOOST_BITSET_CHAR
+
+#endif // include guard
+