dynamic_bitset<Block, Allocator> - 1.88.0 (original) (raw)

The dynamic_bitset class represents a set of bits. It provides accesses to the value of individual bits via anoperator[] and provides all of the bitwise operators that one can apply to builtin integers, such asoperator& and operator<<. The number of bits in the set is specified at runtime via a parameter to the constructor of the dynamic_bitset.

The dynamic_bitset class is nearly identical to thestd::bitsetclass. The difference is that the size of thedynamic_bitset (the number of bits) is specified at run-time during the construction of a dynamic_bitsetobject, whereas the size of a std::bitset is specified at compile-time through an integer template parameter.

The main problem that dynamic_bitset is designed to solve is that of representing a subset of a finite set. Each bit represents whether an element of the finite set is in the subset or not. As such the bitwise operations ofdynamic_bitset, such as operator& andoperator|, correspond to set operations, such as intersection and union.

Synopsis

namespace boost {

template <typename Block, typename Allocator> class dynamic_bitset { public: typedef Block block_type; typedef Allocator allocator_type; typedef implementation-defined size_type;

static const int [bits_per_block](#bits%5Fper%5Fblock) = _implementation-defined_;
static const size_type [npos](#npos) = _implementation-defined_;

class [reference](#reference)
{
    void operator&(); // not defined

public:
    // An automatically generated copy constructor.

    reference& operator=(bool value);
    reference& operator=(const reference& rhs);

    reference& operator|=(bool value);
    reference& operator&=(bool value);
    reference& operator^=(bool value);
    reference& operator-=(bool value);

    bool operator~() const;
    operator bool() const;
    reference& flip();
};

typedef bool [const_reference](#const%5Freference);

[dynamic_bitset](#cons0)();

explicit [dynamic_bitset](#cons1)(const Allocator& alloc);

explicit [dynamic_bitset](#cons2)(size_type num_bits, unsigned long value = 0,
                        const Allocator& alloc = Allocator());

template <typename CharT, typename Traits, typename Alloc>
explicit [dynamic_bitset](#cons3)(const std::basic_string<CharT, Traits, Alloc>& s,
    typename std::basic_string<CharT, Traits, Alloc>::size_type pos = 0,
    typename std::basic_string<CharT, Traits, Alloc>::size_type n = std::basic_string<CharT, Traits, Alloc>::npos,
    const Allocator& alloc = Allocator());

template <typename BlockInputIterator>
[dynamic_bitset](#cons4)(BlockInputIterator first, BlockInputIterator last,
               const Allocator& alloc = Allocator());

[dynamic_bitset](#cons5)(const dynamic_bitset& b);

[dynamic_bitset](#move-cons)(dynamic_bitset&& b);

void [swap](#swap)(dynamic_bitset& b);

dynamic_bitset& [operator=](#assign)(const dynamic_bitset& b);

dynamic_bitset& [operator=](#move-assign)(dynamic_bitset&& b);

allocator_type [get_allocator()](#get%5Fallocator) const;

void [resize](#resize)(size_type num_bits, bool value = false);
void [clear](#clear)();
void [pop_back](#pop%5Fback)();
void [push_back](#push%5Fback)(bool bit);
void [append](#append1)(Block block);

template <typename BlockInputIterator>
void [append](#append2)(BlockInputIterator first, BlockInputIterator last);

dynamic_bitset& [operator&=](#op-and-assign)(const dynamic_bitset& b);
dynamic_bitset& [operator|=](#op-or-assign)(const dynamic_bitset& b);
dynamic_bitset& [operator^=](#op-xor-assign)(const dynamic_bitset& b);
dynamic_bitset& [operator-=](#op-sub-assign)(const dynamic_bitset& b);
dynamic_bitset& [operator<<=](#op-sl-assign)(size_type n);
dynamic_bitset& [operator>>=](#op-sr-assign)(size_type n);
dynamic_bitset [operator<<](#op-sl)(size_type n) const;
dynamic_bitset [operator>>](#op-sr)(size_type n) const;

dynamic_bitset& [set](#set3)(size_type n, size_type len, bool val);
dynamic_bitset& [set](#set2)(size_type n, bool val = true);
dynamic_bitset& [set](#set1)();
dynamic_bitset& [reset](#reset3)(size_type n, size_type len);
dynamic_bitset& [reset](#reset2)(size_type n);
dynamic_bitset& [reset](#reset1)();
dynamic_bitset& [flip](#flip3)(size_type n, size_type len);
dynamic_bitset& [flip](#flip2)(size_type n);
dynamic_bitset& [flip](#flip1)();
reference [at](#at)(size_type n);
bool [at](#const-at)(size_type n) const;
bool [test](#test)(size_type n) const;
bool [test_set](#test)(size_type n, bool val = true);
bool [all](#all)() const;
bool [any](#any)() const;
bool [none](#none)() const;
dynamic_bitset [operator~](#op-not)() const;
size_type [count](#count)() const noexcept;

reference [operator[]](#bracket)(size_type pos);
bool [operator[]](#const-bracket)(size_type pos) const;

unsigned long [to_ulong](#to%5Fulong)() const;

size_type [size](#size)() const noexcept;
size_type [num_blocks](#num%5Fblocks)() const noexcept;
size_type [max_size](#max%5Fsize)() const noexcept;
bool [empty](#empty)() const noexcept;
size_type [capacity](#capacity)() const noexcept;
void [reserve](#reserve)(size_type num_bits);
void [shrink_to_fit](#shrink%5Fto%5Ffit)();

bool [is_subset_of](#is%5Fsubset%5Fof)(const dynamic_bitset& a) const;
bool [is_proper_subset_of](#is%5Fproper%5Fsubset%5Fof)(const dynamic_bitset& a) const;
bool [intersects](#intersects)(const dynamic_bitset& a) const;

size_type [find_first](#find%5Ffirst)() const;
size_type [find_first](#find%5Ffirst%5Foff)(size_type pos) const;
size_type [find_next](#find%5Fnext)(size_type pos) const;

};

template <typename B, typename A> bool operator==(const dynamic_bitset<B, A>& a, const dynamic_bitset<B, A>& b);

template <typename Block, typename Allocator> bool operator!=(const dynamic_bitset<Block, Allocator>& a, const dynamic_bitset<Block, Allocator>& b);

template <typename B, typename A> bool operator<(const dynamic_bitset<B, A>& a, const dynamic_bitset<B, A>& 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);

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);

template <typename Block, typename Allocator, typename CharT, typename Alloc> void to_string(const dynamic_bitset<Block, Allocator>& b, std::basic_string<CharT, Alloc>& s);

template <typename Block, typename Allocator, typename BlockOutputIterator> void to_block_range(const dynamic_bitset<Block, Allocator>& b, BlockOutputIterator result);

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);

} // namespace boost

Definitions

Each bit represents either the Boolean value true or false (1 or 0). To set a bit is to assign it 1. To clear or_reset_ a bit is to assign it 0. To flip a bit is to change the value to 1 if it was 0 and to 0 if it was 1. Each bit has a non-negative position. A bitset x containsx.size() bits, with each bit assigned a unique position in the range [0,x.size()). The bit at position 0 is called the least significant bit and the bit at positionsize() - 1 is the most significant bit. When converting an instance of dynamic_bitset to or from an unsigned long n, the bit at position i of the bitset has the same value as (n >> i) & 1.

Examples

Example 1 (setting and reading some bits)

Example 2 (creating some bitsets from integers)

Example 3 (performing input/output and some bitwise operations).

Rationale

dynamic_bitset is not a Container and does not provide iterators for the following reason:

A container with a proxy reference type can not fulfill the container requirements as specified in the C++ standard (unless one resorts to strange iterator semantics).std::vector has a proxy referencetype and does not fulfill the container requirements and as a result has caused many problems. One common problem is when people try to use iterators from std::vectorwith a Standard algorithm such as std::search. Thestd::search requirements say that the iterator must be aForward Iterator, but the std::vector::iteratordoes not meet this requirement because of the proxy reference. Depending on the implementation, they may or not be a compile error or even a run-time error due to this misuse. For further discussion of the problem see Effective STL by Scott Meyers). So dynamic_bitset tries to avoid these problems by not pretending to be a container.

Some people prefer the name "toggle" to "flip". The name "flip" was chosen because that is the name used in std::bitset. In fact, most of the function names for dynamic_bitsetwere chosen for this reason.

dynamic_bitset does not throw exceptions when a precondition is violated (as is done in std::bitset). Instead assert is used. See the guidelines for Error and Exception Handlingfor the explanation.

Header Files

The class dynamic_bitset is defined in the header boost/dynamic_bitset.hpp. Also, there is a forward declaration for dynamic_bitsetin the header boost/dynamic_bitset_fwd.hpp.

Template parameters

Parameter	Description	Default
Block	The integer type in which the bits are stored.	unsigned long
Allocator	The allocator type used for all internal memory management.	std::allocator

Concepts Modeled

Assignable, Default Constructible, Equality Comparable, LessThan Comparable.

Type requirements

Block

is an unsigned integer type.

Allocator

satisfies the Standard requirements for an allocator.

Public base classes

None.

Nested type names

dynamic_bitset::reference

A proxy class that acts as a reference to a single bit. It contains an assignment operator, a conversion to bool, an operator~, and a member function flip. It exists only as a helper class for dynamic_bitset'soperator[]. The following table describes the valid operations on the reference type. Assume that bis an instance of dynamic_bitset, i, j are ofsize_type and in the range [0,b.size()). Also, note that when we write b[i] we mean an object of typereference that was initialized from b[i]. The variable x is a bool.

Expression	Semantics
x = b[i]	Assign the ith bit of b to x.
(bool)b[i]	Return the ith bit of b.
b[i] = x	Set the ith bit of b to the value of x and return b[i].
b[i] \|= x	Or the ith bit of b with the value of x and return b[i].
b[i] &= x	And the ith bit of b with the value of xand return b[i].
b[i] ^= x	Exclusive-Or the ith bit of b with the value ofx and return b[i].
b[i] -= x	If x==true, clear the ith bit of b. Returnsb[i].
b[i] = b[j]	Set the ith bit of b to the value of the jth bit ofb and return b[i].
b[i] \|= b[j]	Or the ith bit of b with the jth bit of band return b[i].
b[i] &= b[j]	And the ith bit of b with the jth bit of b and return b[i].
b[i] ^= b[j]	Exclusive-Or the ith bit of b with the jth bit of b and return b[i].
b[i] -= b[j]	If the jth bit of b is set, clear the ith bit of b. Returns b[i].
x = ~b[i]	Assign the opposite of the ith bit of b to x.
(bool)~b[i]	Return the opposite of the ith bit of b.
b[i].flip()	Flip the ith bit of b and return b[i].

dynamic_bitset::const_reference

The type

bool

dynamic_bitset::size_type

The unsigned integer type for representing the size of the bit set.

dynamic_bitset::block_type

The same type as

Block

dynamic_bitset::allocator_type;

The same type as

Allocator

Public data members

dynamic_bitset::bits_per_block

The number of bits the type

Block

uses to represent values, excluding any padding bits. Numerically equal to

std::numeric_limits::digits

dynamic_bitset::npos

The maximum value of

size_type

Constructors

dynamic_bitset()

Effects: Constructs a bitset of size zero. The allocator for this bitset is a default-constructed object of type

Allocator

.
Postconditions:

this->size() == 0

.
Throws: Nothing unless the default constructor of

Allocator

throws an exception.
(Required by Default Constructible.)

dynamic_bitset(const Allocator& alloc)

Effects: Constructs a bitset of size zero. A copy of the

alloc

object will be used in subsequent bitset operations such as

resize

to allocate memory.
Postconditions:

this->size() == 0

.
Throws: nothing.

dynamic_bitset(size_type num_bits, unsigned long value = 0, const Allocator& alloc = Allocator())

Effects: Constructs a bitset from an integer. The first

bits are initialized to the corresponding bits in

value

and all other bits, if any, to zero (where

M = min(num_bits, std::numeric_limits::digits)

). A copy of the

alloc

object will be used in subsequent bitset operations such as

resize

to allocate memory. Note that, e.g., the following

dynamic_bitset b<>( 16, 7 );

will match the constructor from an iterator range (not this one), but the underlying implementation will still "do the right thing" and construct a bitset of 16 bits, from the value 7.
Postconditions:

this->size() == num_bits
For all i in the range [0,M),(*this)[i] == (value >> i) & 1.
For all i in the range [M,num_bits),(*this)[i] == false.

Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

dynamic_bitset(const dynamic_bitset& x)

Effects: Constructs a bitset that is a copy of the bitset

. The allocator for this bitset is a copy of the allocator in

.
Postconditions: For all

in the range

[0,x.size())

(*this)[i] == x[i]

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

).
(Required by Assignable.)

dynamic_bitset(dynamic_bitset&& x)

Effects: Constructs a bitset that is the same as the bitset

, while using the resources from

. The allocator for this bitset is moved from the allocator in

.
Postconditions: For all

in the range

[0,x.size())

(*this)[i] == x[i]

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

template explicit dynamic_bitset(BlockInputIterator first, BlockInputIterator last, const Allocator& alloc = Allocator());

Effects:

If this constructor is called with a type BlockInputIterator which_is actually an integral type_, the library behaves as if the constructor from unsigned long were called, with argumentsstatic_cast<size_type>(first), last and alloc, in that order.
Example:
// b is constructed as if by calling the constructor
//
// dynamic_bitset(size_type num_bits,
// unsigned long value = 0,

// const Allocator& alloc = Allocator())
//
// with arguments
//
// static_cast<dynamic_bitset::size_type>(8),
// 7,
// Allocator()
//
dynamic_bitset b(8, 7);

Note:
At the time of writing (October 2008) this is aligned with the proposed resolution for library issue 438. That is a _post C++03_change, and is currently in the working paper forC++0x. Informally speaking, the critical changes with respect to C++03 are the drop of a static_caston the second argument, and more leeway as to when the templated constructor should have the same effect as the (size, value) one: only when InputIterator is an integral type, in C++03; when it is either an integral type or any other type that the implementation might detect as impossible to be an input iterator, with the proposed resolution. For the purposes of dynamic_bitset we limit ourselves to the first of these two changes.

Otherwise (i.e. if the template argument is not an integral type), constructs—under the condition in therequires clause—a bitset based on a range of blocks. Let *first be block number 0, *++firstblock number 1, etc. Block number b is used to initialize the bits of the dynamic_bitset in the position range[b*bits_per_block, (b+1)*bits_per_block). For each block number b with value bval, the bit(bval >> i) & 1 corresponds to the bit at position (b * bits_per_block + i) in the bitset (wherei goes through the range [0, bits_per_block)).

Requires:

BlockInputIterator

must be either an integral type or a model of Input Iterator whose

value_type

is the same type as

Block

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

template<typename Char, typename Traits, typename Alloc> explicit dynamic_bitset(const std::basic_string<Char,Traits,Alloc>& s, typename std::basic_string<CharT, Traits, Alloc>::size_type pos = 0, typename std::basic_string<CharT, Traits, Alloc>::size_type n = std::basic_string<Char,Traits,Alloc>::npos, const Allocator& alloc = Allocator())

Precondition:

pos <= s.size()

and the characters used to initialize the bits must be

.
Effects: Constructs a bitset from a string of 0's and 1's. The first

bits are initialized to the corresponding characters in

, where

M = min(s.size() - pos, n)

. Note that the _highest_character position in

, not the lowest, corresponds to the least significant bit. That is, character position

pos + M - 1 - i

corresponds to bit

. So, for example,

dynamic_bitset(string("1101"))

is the same as

dynamic_bitset(13ul)

.
Throws: an allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

Destructor

~dynamic_bitset()

Effects: Releases the memory associated with this bitset and destroys the bitset object itself.
Throws: nothing.

Member Functions

void swap(dynamic_bitset& b);

Effects: The contents of this bitset and bitset

are exchanged.
Postconditions: This bitset is equal to the original

, and

is equal to the previous version of this bitset.
Throws: nothing.

dynamic_bitset& operator=(const dynamic_bitset& x)

Effects: This bitset becomes a copy of the bitset

.
Postconditions: For all

in the range

[0,x.size())

(*this)[i] == x[i]

.
Returns:

*this

.
Throws: nothing.
(Required by Assignable.)

dynamic_bitset& operator=(dynamic_bitset&& x)

Effects: This bitset becomes the same as the bitset

, while using the resources from

.
Postconditions: For all

in the range

[0,x.size())

(*this)[i] == x[i]

.
Returns:

*this

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

allocator_type get_allocator() const;

Returns: A copy of the allocator object used to construct

*this

void resize(size_type num_bits, bool value = false);

Effects: Changes the number of bits of the bitset to

num_bits

. If

num_bits > size()

then the bits in the range

[0,size())

remain the same, and the bits in

[size(),num_bits)

are all set to

value

. If

num_bits < size()

then the bits in the range

[0,num_bits)

stay the same (and the remaining bits are discarded).
Postconditions:

this->size() == num_bits

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

void clear()

Effects: The size of the bitset becomes zero.
Throws: nothing.

void pop_back();

Precondition:

!this->empty()

.
Effects: Decreases the size of the bitset by one.
Throws: nothing.

void push_back(bool value);

Effects: Increases the size of the bitset by one, and sets the value of the new most-significant bit to

value

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

void append(Block value);

Effects: Appends the bits in

value

to the bitset (appends to the most-significant end). This increases the size of the bitset by

bits_per_block

. Let

be the old size of the bitset, then for

in the range

[0,bits_per_block)

, the bit at position

(s + i)

is set to

((value >> i) & 1)

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

template void append(BlockInputIterator first, BlockInputIterator last);

Effects: This function provides the same end result as the following code, but is typically more efficient.

for (; first != last; ++first) append(*first);

Requires: The

BlockInputIterator

type must be a model of Input Iterator and the

value_type

must be the same type as

Block

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

dynamic_bitset& operator&=(const dynamic_bitset& rhs)

Requires:

this->size() == rhs.size()

.
Effects: Bitwise-AND all the bits in

rhs

with the bits in this bitset. This is equivalent to:

for (size_type i = 0; i != this->size(); ++i) (*this)[i] = (*this)[i] & rhs[i];

Returns:

*this

.
Throws: nothing.

dynamic_bitset& operator|=(const dynamic_bitset& rhs)

Requires:

this->size() == rhs.size()

.
Effects: Bitwise-OR's all the bits in

rhs

with the bits in this bitset. This is equivalent to:

for (size_type i = 0; i != this->size(); ++i) (*this)[i] = (*this)[i] | rhs[i];

Returns:

*this

.
Throws: nothing.

dynamic_bitset& operator^=(const dynamic_bitset& rhs)

Requires:

this->size() == rhs.size()

.
Effects: Bitwise-XOR's all the bits in

rhs

with the bits in this bitset. This is equivalent to:

for (size_type i = 0; i != this->size(); ++i) (*this)[i] = (*this)[i] ^ rhs[i];

Returns:

*this

.
Throws: nothing.

dynamic_bitset& operator-=(const dynamic_bitset& rhs)

Requires:

this->size() == rhs.size()

.
Effects: Computes the set difference of this bitset and the

rhs

bitset. This is equivalent to:

for (size_type i = 0; i != this->size(); ++i) (*this)[i] = (*this)[i] && !rhs[i];

Returns:

*this

.
Throws: nothing.

dynamic_bitset& operator<<=(size_type n)

Effects: Shifts the bits in this bitset to the left by

bits. For each bit in the bitset, the bit at position pos takes on the previous value of the bit at position

pos - n

, or zero if no such bit exists.
Returns:

*this

.
Throws: nothing.

dynamic_bitset& operator>>=(size_type n)

Effects: Shifts the bits in this bitset to the right by

bits. For each bit in the bitset, the bit at position

pos

takes on the previous value of bit

pos + n

, or zero if no such bit exists.
Returns:

*this

.
Throws: nothing.

dynamic_bitset operator<<(size_type n) const

Returns: a copy of

*this

shifted to the left by

bits. For each bit in the returned bitset, the bit at position pos takes on the value of the bit at position

pos - n

of this bitset, or zero if no such bit exists.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

dynamic_bitset operator>>(size_type n) const

Returns: a copy of

*this

shifted to the right by

bits. For each bit in the returned bitset, the bit at position pos takes on the value of the bit at position

pos + n

of this bitset, or zero if no such bit exists.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

dynamic_bitset& set()

Effects: Sets every bit in this bitset to 1.
Returns:

*this

Throws: nothing.

dynamic_bitset& flip()

Effects: Flips the value of every bit in this bitset.
Returns:

*this

Throws: nothing.

dynamic_bitset operator~() const

Returns: a copy of

*this

with all of its bits flipped.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

dynamic_bitset& reset()

Effects: Clears every bit in this bitset.
Returns:

*this

Throws: nothing.

dynamic_bitset& set(size_type n, size_type len, bool val);

Precondition:

n + len < this->size()

.
Effects: Sets every bit indexed from

n + len - 1

inclusively if

val

true

, and clears them if

val

false

.
Returns:

*this

dynamic_bitset& set(size_type n, bool val = true)

Precondition:

n < this->size()

.
Effects: Sets bit

val

true

, and clears bit

val

false

.
Returns:

*this

dynamic_bitset& reset(size_type n, size_type len);

Precondition:

n + len < this->size()

.
Effects: Clears every bit indexed from

n + len - 1

inclusively.
Returns:

*this

dynamic_bitset& reset(size_type n)

Precondition:

n < this->size()

.
Effects: Clears bit

.
Returns:

*this

dynamic_bitset& flip(size_type n, size_type len)

Precondition:

n + len < this->size()

.
Effects: Flips every bit indexed from

n + len - 1

inclusively.
Returns:

*this

dynamic_bitset& flip(size_type n)

Precondition:

n < this->size()

.
Effects: Flips bit

.
Returns:

*this

size_type size() const

Returns: the number of bits in this bitset.
Throws: nothing.

size_type num_blocks() const

Returns: the number of blocks in this bitset.
Throws: nothing.

size_type max_size() const;

Returns: the maximum size of a

dynamic_bitset

object having the same type as

*this

. Note that if any

dynamic_bitset

operation causes

size()

to exceed

max_size()

then the behavior is undefined.

[The semantics of this function could change slightly when lib issue 197 will be closed]

bool empty() const;

Returns:

true

this->size() == 0

false

otherwise. Note: not to be confused with

none()

, that has different semantics.

size_type capacity() const;

Returns: The total number of elements that

*this

can hold without requiring reallocation.
Throws: nothing.

void reserve(size_type num_bits);

Effects: A directive that informs the bitset of a planned change in size, so that it can manage the storage allocation accordingly. After reserve(), capacity() is greater or equal to the argument of reserve() if reallocation happens; and equal to the previous value of capacity() otherwise. Reallocation happens at this point if and only if the current capacity is less than the argument of reserve().
Note: It does not change the size() of the bitset.
Postcondtitions:

this->capacity() >= num_bits

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

void shrink_to_fit();

Effects: shrink_to_fit() is a request to reduce memory use by removing unused capacity.
Note: It does not change the size() of the bitset.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

size_type count() const

Returns: the number of bits in this bitset that are set.
Throws: nothing.

bool all() const

Returns:

true

if all bits in this bitset are set or if

size() == 0

, and otherwise returns

false

.
Throws: nothing.

bool any() const

Returns:

true

if any bits in this bitset are set, and otherwise returns

false

.
Throws: nothing.

bool none() const

Returns:

true

if no bits are set, and otherwise returns

false

.
Throws: nothing.

reference at(size_type n)

Precondition:

n < this->size()

.
Returns: The same as

operator[](n)

.
Throws:

std::out_of_range

if that

is not within the range of the bitset.

bool at(size_type n) const

Precondition:

n < this->size()

.
Returns: The same as

operator[](n)

.
Throws:

std::out_of_range

if that

is not within the range of the bitset.

bool test(size_type n) const

Precondition:

n < this->size()

.
Returns:

true

if bit

is set and

false

is bit

is 0.

bool test_set(size_type n, bool val = true)

Precondition:

n < this->size()

.
Effects: Sets bit

val

true

, and clears bit

val

false

.
Returns:

true

if the previous state of bit

was set and

false

is bit

is 0.

reference operator[](size_type n)

Precondition:

n < this->size()

.
Returns: a

reference

to bit

. Note that

reference

is a proxy class with an assignment operator and a conversion to

bool

, which allows you to use

operator[]

for assignment. That is, you can write both

x = b[n]

and

b[n] = x

. However, in many other respects the proxy is not the same as the true reference type

bool&

bool operator[](size_type n) const

Precondition:

n < this->size()

.
Returns: The same as

test(n)

unsigned long to_ulong() const

Returns: The numeric value corresponding to the bits in

*this

.
Throws:

std::overflow_error

if that value is too large to be represented in an

unsigned long

, i.e. if

*this

has any non-zero bit at a position

>= std::numeric_limits::digits

bool is_subset_of(const dynamic_bitset& a) const

Requires:

this->size() == a.size()

Returns: true if this bitset is a subset of bitset

. That is, it returns true if, for every bit that is set in this bitset, the corresponding bit in bitset

is also set. Otherwise this function returns false.
Throws: nothing.

bool is_proper_subset_of(const dynamic_bitset& a) const

Requires:

this->size() == a.size()

Returns: true if this bitset is a proper subset of bitset

. That is, it returns true if, for every bit that is set in this bitset, the corresponding bit in bitset

is also set and if

this->count() < a.count()

. Otherwise this function returns false.
Throws: nothing.

bool intersects(const dynamic_bitset& a) const

Requires:

this->size() == a.size()

Returns: true if this bitset and

intersect. That is, it returns true if, there is a bit which is set in this bitset, such that the corresponding bit in bitset

is also set. Otherwise this function returns false.
Throws: nothing.

size_type find_first() const;

Returns: the lowest index

such as bit

is set, or

npos

*this

has no on bits.

size_type find_first(size_type pos) const;

Returns: the lowest index

greater or equal to

offset

such as bit

is set, or

npos

if no such index exists.

size_type find_next(size_type pos) const;

Returns: the lowest index

greater than

pos

such as bit

is set, or

npos

if no such index exists.

bool operator==(const dynamic_bitset& rhs) const

Returns:

true

this->size() == rhs.size()

and if for all

in the range

[0,rhs.size())

(*this)[i] == rhs[i]

. Otherwise returns

false

.
Throws: nothing.
(Required by Equality Comparable.)

bool operator!=(const dynamic_bitset& rhs) const

Returns:

!((*this) == rhs)

Throws: nothing.
(Required by Equality Comparable.)

bool operator<(const dynamic_bitset& rhs) const

Returns:

true

if this bitset is lexicographically less than

rhs

, and returns

false

otherwise. (See the description of lexicographical_comparefor a definition of lexicographic ordering).
Throws: nothing.
(Required by Less Than Comparable.)

bool operator>(const dynamic_bitset& rhs) const

Returns:

!((*this) < rhs || (*this) == rhs)

Throws: nothing.
(Required by Less Than Comparable.)

bool operator<=(const dynamic_bitset& rhs) const

Returns:

(*this) < rhs || (*this) == rhs

Throws: nothing.
(Required by Less Than Comparable.)

bool operator>=(const dynamic_bitset& rhs) const

Returns:

(*this) > rhs || (*this) == rhs

Throws: nothing.
(Required by Less Than Comparable.)

Non-Member Functions

dynamic_bitset operator&(const dynamic_bitset& a, const dynamic_bitset& b)

Requires:

a.size() == b.size()

Returns: A new bitset that is the bitwise-AND of the bitsets

and

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

dynamic_bitset operator|(const dynamic_bitset& a, const dynamic_bitset& b)

Requires:

a.size() == b.size()

Returns: A new bitset that is the bitwise-OR of the bitsets

and

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

dynamic_bitset operator^(const dynamic_bitset& a, const dynamic_bitset& b)

Requires:

a.size() == b.size()

Returns: A new bitset that is the bitwise-XOR of the bitsets

and

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

dynamic_bitset operator-(const dynamic_bitset& a, const dynamic_bitset& b)

Requires:

a.size() == b.size()

Returns: A new bitset that is the set difference of the bitsets

and

.
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

template <typename CharT, typename Alloc> void to_string(const dynamic_bitset<Block, Allocator>& b, std::basic_string<Char,Traits,Alloc>& s)

Effects: Copies a representation of

into the string

. A character in the string is

'1'

if the corresponding bit is set, and

'0'

if it is not. Character position

in the string corresponds to bit position

b.size() - 1 - i

.
Throws: If memory is exhausted, the string will throw an allocation error.
Rationale: This function is not a member function taking zero arguments and returning a string for a couple reasons. First, this version can be slighly more efficient because the string is not copied (due to being passed by value). Second, as a member function, to allow for flexibility with regards to the template parameters of

basic_string

, the member function would require explicit template parameters. Few C++ programmers are familiar with explicit template parameters, and some C++ compilers do not handle them properly.

template <typename Block, typename Alloc, typename BlockOutputIterator> void to_block_range(const dynamic_bitset<Block, Alloc>& b, BlockOutputIterator result)

Effects: Writes the bits of the bitset into the iterator

result

a block at a time. The first block written represents the bits in the position range

[0,bits_per_block)

in the bitset, the second block written the bits in the range

[bits_pre_block,2*bits_per_block)

, and so on. For each block

bval

written, the bit

(bval >> i) & 1

corresponds to the bit at position

(b * bits_per_block + i)

in the bitset.
Requires: The type

BlockOutputIterator

must be a model of Output Iterator and its

value_type

must be the same type as

Block

. Further, the size of the output range must be greater or equal

b.num_blocks()

template <typename BlockIterator, typename Block, typename Alloc> void from_block_range(BlockIterator first, BlockIterator last, const dynamic_bitset<Block, Alloc>& b)

Effects: Reads blocks from the iterator range into the bitset.
Requires: The type

BlockIterator

must be a model of Input Iterator and its

value_type

must be the same type as

Block

. The size of the iterator range must be less or equal to

b.num_blocks()

template <typename Char, typename Traits, typename Block, typename Alloc> basic_ostream<Char, Traits>& operator<<(basic_ostream<Char, Traits>& os, const dynamic_bitset<Block, Alloc>& b)

Effects: Inserts a textual representation of b into the stream

(highest bit first). Informally, the output is the same as doing

std::basic_string<Char, Traits> s; boost::to_string(x, s): os << s;

except that the stream inserter takes into accout the locale imbued into

, which

boost::to_string()

can't do. Here is a more precise specification, given in terms of "as if" rule: first, for each valid position i into the bitset

let's put:

character_of(b[i)]) = b[i]? os.widen('1') : os.widen('0');

Let also

be a

std::basic_string<Char, Traits>

object, having length

b.size()

and such as, for each

[0, b.size())

s[i] is character_of(b[i])

Then, the output, the effects on

and the exception behavior is the same as outputting the object

(same width, same exception mask, same padding, same setstate() logic)
Returns: os
Throws:

std::ios_base::failure

if there is a problem writing to the stream.

template <typename Char, typename Traits, typename Block, typename Alloc> std::basic_istream<Char,Traits>& operator>>(std::basic_istream<Char,Traits>& is, dynamic_bitset<Block, Alloc>& b)

Effects: Extracts a

dynamic_bitset

from an input stream.

Definitions:

Let Tr be the traits_type of is. Then:

A (non-eof) character c extracted from is is a bitset digit if and only if either Tr::eq(c, is.widen('0')) or Tr::eq(c, is.widen('1')) return true.
If c is a bitset digit, it's corresponding bit value is 0 if Tr::eq(c, is.widen('0')) is true, 1 otherwise.

The function begins by constructing a

sentry

object

as if

were constructed by

typename std::basic_istream<Char, Traits>::sentry k(is)

. If

bool(k)

is true, it calls

b.clear()

then attempts to extract characters from

. For each character c that is a bitset digit the corresponding bit value is appended to the less significant end of

(appending may throw). If

is.width()

is greater than zero and smaller than

b.max_size()

then the maximum number

of bits appended is

is.width()

; otherwise

b.max_size()

. Unless the extractor is exited via an exception, characters are extracted (and corresponding bits appended) until any of the following occurs:

n bits are stored into the bitset;
end-of-file, or an error, occurs on the input sequence;
the next available input character isn't a bitset digit

If no exception caused the function to exit then

is.width(0)

is called, regardless of how many characters were actually extracted. The sentry object k is destroyed.

If the function extracts no characters[???], it calls is.setstate(std::ios::failbit), which may throw

std::ios_base::failure

.
------
Throws: An allocation error if memory is exhausted (

std::bad_alloc

Allocator=std::allocator

). A

std::ios_base::failure

if there is a problem reading from the stream.

Exception guarantees

All of

dynamic_bitset

functions offer at least the basic exception guarantee.

Changes from previous version(s)

Changes in Boost 1.56.0

Support for C++11 move constructors.
Warning fixes on MSVC 2013.
Support for C++11 minimal allocators.
Add noexcept specifications.

Changes in Boost 1.37.0

The constructor from a block range implements a "do the right thing" behavior, a la standard sequences.

Changes from Boost 1.31.0

The stream extractor has completely different semantics: as natural for a dynamic structure, it now expands the bitset as needed during extraction. The new behaviour mimics that of the basic_stringextractor but there are some differences the user should be aware of; so, please, check the documentation. (One difference concerns the case where stream.width() > bitset.max_size() > 0. In that circumstance the extractor of dynamic_bitset never attempts to extract more than max_size() characters, whereas the extractor ofbasic_string goes on and, on conforming implementations, eventually throws a length_error exception. Note: That's what the standard mandates -see especially library issue 83- but not all implementations conform)
The stream extractor is now also "exception-aware" in the sense that it works correctly when setting exception masks on the stream.
Several member functions (empty(), find_first(), find_next(), get_allocator(), intersects(), max_size() ) have been added.
The constructor from basic_string has a new parameter that was totally forgotten before.

Technicalities and minor changes

The class reference has been reimplemented so that dynamic_bitset's references behave more like references to standard container elements. In particular it is now guaranteed that they cannot be invalidated from a standard library swap() function applied to their corresponding dynamic_bitsets.

General improvements

Several optimizations to member and non-member functions and to the nested class reference.

Acknowledgements

We would like to thank the Boost community for putting in the time to review and accept this library. This library is much better than it ever would have been due to all the suggestions from Boost members. We especially thank Matt Marcus for taking on the task of review manager. Also, a special thanks goes to James Kanze for his invaluable help with the internationalization issues.

Copyright © 2001	Jeremy Siek, Indiana University (jsiek@osl.iu.edu) Chuck Allison, Senior Editor, C/C++ Users Journal (cda@freshsources.com)
Copyright © 2003-2004, 2008	Gennaro Prota (name.surname yahoo.com)
Copyright © 2014	Ahmed Charles (acharles@outlook.com)
Copyright © 2014	Glen Fernandes (glenjofe@gmail.com)
Copyright © 2014	Riccardo Marcangelo (ricky.65@outlook.com)

dynamic_bitset<Block, Allocator> - 1.88.0 (original) (raw)

Contents

Description

Synopsis

Definitions

Examples

Rationale

Header Files

Template parameters

Concepts Modeled

Type requirements

Public base classes

Nested type names

Public data members

Constructors

Destructor

Member Functions

Non-Member Functions

Exception guarantees

Changes from previous version(s)

Changes in Boost 1.56.0

Changes in Boost 1.37.0

Changes from Boost 1.31.0

See also

Acknowledgements