std::bitset<N>::bitset

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bitset::bitset

bitset::operator==bitset::operator!=

(until C++20)

Element access

bitset::operator[]

bitset::test

bitset::allbitset::anybitset::none

(C++11)

bitset::operator&=bitset::operator|=bitset::operator^=bitset::operator~

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bitset();	(1)	(noexcept since C++11) (constexpr since C++11)
	(2)
bitset(unsignedlong val);			(until C++11)
constexpr bitset(unsignedlonglong val)noexcept;			(since C++11)
template<class CharT,class Traits,class Alloc> explicit bitset (conststd::basic_string<CharT, Traits, Alloc>& str, typenamestd::basic_string <CharT, Traits, Alloc>::size_type pos=0, typenamestd::basic_string<CharT, Traits, Alloc>::size_type n=std::basic_string<CharT, Traits, Alloc>::npos, CharT zero= CharT('0'), CharT one= CharT('1'));		(3)	(constexpr since C++23)
template<class CharT,class Traits> constexprexplicit bitset (std::basic_string_view<CharT, Traits> str, std::size_t pos=0,std::size_t n=std::size_t(-1), CharT zero= CharT('0'), CharT one= CharT('1'));		(4)	(since C++26)
template<class CharT> explicit bitset(const CharT* str,std::size_t n=std::size_t(-1), CharT zero= CharT('0'), CharT one= CharT('1'));		(5)	(since C++11) (constexpr since C++23)

Constructs a new bitset from one of several optional data sources:

1) Default constructor. Constructs a bitset with all bits set to zero.

2) Constructs a bitset from an unsigned integerval.

Given the number of bits in thevalue representation ofunsignedlong(until C++11)unsignedlonglong(since C++11) asS:

The first (rightmost, least significant)std::min(S, N) bit positions are initialized with the corresponding bit values ofval.
IfS is less thanN, the remaining bit positions are initialized to zeroes.

3) Constructs a bitset using the characters instr. An optional starting positionpos and lengthn can be provided, as well as characters denoting alternate values for set (one) and unset (zero) bits.Traits::eq() is used to compare the character values.

The effective length of the initializing string isstd::min(n, str.size()- pos).

4) Similar to(3), but uses astd::basic_string_view instead of astd::basic_string.

5) Similar to(3), but uses aconst CharT* instead of astd::basic_string.

Equivalent tobitset(n==std::basic_string<CharT>::npos ?std::basic_string<CharT>(str) :std::basic_string<CharT>(str, n),0, n, zero, one).	(until C++26)
Equivalent tobitset(n==std::basic_string_view<CharT>::npos ?std::basic_string_view<CharT>(str) :std::basic_string_view<CharT>(str, n),0, n, zero, one).	(since C++26)

[edit]Parameters

val	-	number used to initialize the bitset
str	-	string used to initialize the bitset
pos	-	a starting offset intostr
n	-	number of characters to use fromstr
zero	-	alternate character for unset bits instr
one	-	alternate character for set bits instr

[edit]Exceptions

3,4)std::out_of_range ifpos> str.size(),std::invalid_argument if any character is notone orzero.

5)std::invalid_argument if any character is notone orzero.

[edit]Notes

Feature-test macro	Value	Std	Feature
`__cpp_lib_constexpr_bitset`	`202207L`	(C++23)	A more constexpr`std::bitset`, overloads(3,5)
`__cpp_lib_bitset`	`202306L`	(C++26)	Interfacing`std::bitset` withstd::string_view,(4)

[edit]Example

Run this code

#include <bitset>#include <climits>#include <iostream>#include <string> int main(){// empty constructor (1)std::bitset<8> b1;// [0,0,0,0,0,0,0,0] // unsigned long long constructor (2)std::bitset<8> b2(42);// [0,0,1,0,1,0,1,0]std::bitset<70> bl(ULLONG_MAX);// [0,0,0,0,0,0,1,1,1,...,1,1,1] in C++11std::bitset<8> bs(0xfff0);// [1,1,1,1,0,0,0,0] // string constructor (3)std::string bit_string="110010";std::bitset<8> b3(bit_string);// [0,0,1,1,0,0,1,0]std::bitset<8> b4(bit_string,2);// [0,0,0,0,0,0,1,0]std::bitset<8> b5(bit_string,2,3);// [0,0,0,0,0,0,0,1] // string constructor using custom zero/one digits (3)std::string alpha_bit_string="aBaaBBaB";std::bitset<8> b6(alpha_bit_string,0, alpha_bit_string.size(),'a','B');// [0,1,0,0,1,1,0,1] // char* constructor using custom digits (5)std::bitset<8> b7("XXXXYYYY",8,'X','Y');// [0,0,0,0,1,1,1,1] std::cout<<"b1: "<< b1<<"\nb2: "<< b2<<"\nbl: "<< bl<<"\nbs: "<< bs<<"\nb3: "<< b3<<"\nb4: "<< b4<<"\nb5: "<< b5<<"\nb6: "<< b6<<"\nb7: "<< b7<<'\n';}

Possible output:

b1: 00000000b2: 00101010bl: 0000001111111111111111111111111111111111111111111111111111111111111111bs: 11110000b3: 00110010b4: 00000010b5: 00000001b6: 01001101b7: 00001111

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 396	C++98	the values of the zero and one characters for overload(3) were0 and1 (which do not correspond to'0' and'1')	added parameters to provide values for these characters
LWG 457	C++98	S wasCHAR_BIT* sizeof(unsignedlong) for overload(2), butunsignedlong is not guaranteed to use all its bits to represent its value	consider the number of bits of the value representation instead
LWG 2250	C++98	the behavior was undefined ifpos> str.size() istrue	always throws an exception in this case