std::bitset::bitset(3) C++ Standard Libary std::bitset::bitset(3) NAME std::bitset::bitset - std::bitset::bitset Synopsis bitset(); (until C++11) constexpr bitset() noexcept; (since C++11) bitset( unsigned long val ); (un- til C++11) constexpr bitset( unsigned long long val ) (since C++11) noexcept; template< class CharT, class Traits, class Alloc > explicit bitset( const std::basic_string<CharT, Traits, Alloc>& str, typename std::basic_string<CharT, Traits, Alloc>::size_type pos = 0, (3) (constexpr since typename std::basic_string<CharT, C++23) Traits, Alloc>::size_type n = std::basic_string<CharT, Traits, Alloc>::npos, CharT zero = CharT('0'), (1) CharT one = CharT('1') ); template< class CharT, class Traits > (2) constexpr explicit bitset( std::basic_string_view<CharT, Traits> str, std::size_t pos = 0, std::size_t n = (4) (since C++26) std::size_t(-1), CharT zero = CharT('0'), CharT one = CharT('1') ); template< class CharT > explicit bitset( const CharT* str, (since C++11) std::size_t n = std::size_t(-1), (5) (constexpr since CharT zero = CharT('0'), C++23) CharT one = CharT('1') ); 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, initializing the first (rightmost, least signif- icant) M bit positions to the corresponding bit values of val, where M is the smaller of * N, and * the number of bits in the value representation of unsigned long. (until C++11) For typical implementations, it is 32 or 64. * the number of bits in the value representation of unsigned long (since C++11) long. For typical implementations, it is 64. If M is less than N, the remaining bit positions are initialized to ze- roes. 3) Constructs a bitset using the characters in the std::basic_string str. An optional starting position pos and length n 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 is std::min(n, str.size() - pos). If pos > str.size(), this constructor throws std::out_of_range. If any character examined in str is not zero or one, this constructor throws std::in- valid_argument. 4) Similar to (3), but uses a std::basic_string_view instead of a std::basic_string. 5) Similar to (3), but uses a const CharT* instead of a std::ba- sic_string. Equivalent to bitset(n == std::size_t(-1) ? basic_string<CharT>(str) : basic_string<CharT>(str, n), 0, n, zero, one) This constructor may dynamically allocate memory, although (until C++26) implementations generally avoid dynamic allocation. This constructor does not dynamically allocate memory, as if only (since C++26) std::basic_string_view is involved. Parameters val - number used to initialize the bitset str - string used to initialize the bitset pos - a starting offset into str n - number of characters to use from str one - alternate character for set bits in str zero - alternate character for unset bits in str Exceptions 3,4) std::out_of_range if pos > str.size(), std::invalid_argument if any character is not one or zero. 5) std::invalid_argument if any character is not one or zero. 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 with std::string_view, (4) 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++11 std::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: 00000000 b2: 00101010 bl: 0000001111111111111111111111111111111111111111111111111111111111111111 bs: 11110000 b3: 00110010 b4: 00000010 b5: 00000001 b6: 01001101 b7: 00001111 Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior the values of the zero and one characters added para- meters to LWG 396 C++98 for overload (3) provide were 0 and 1 (which do not correspond to values for these '0' and '1') characters M is the smaller of N and the value CHAR_BIT * sizeof(unsigned long) consider the number LWG 457 C++98 for overload (2), but unsigned long is of bits of the value not representa- tion instead guaranteed to use all its bits to represent its value See also set sets bits to true or given value (public member function) reset sets bits to false (public member function) http://cppreference.com 2024.06.10 std::bitset::bitset(3)
NAME | Synopsis | Parameters | Exceptions | Notes | Example | Possible output: | See also
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