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std::bitset::test(3) C++ Standard Libary std::bitset::test(3) NAME std::bitset::test - std::bitset::test Synopsis bool test( std::size_t pos ) const; (constexpr since C++23) Returns the value of the bit at the position pos (counting from 0). Unlike operator[], performs a bounds check and throws std::out_of_range if pos does not correspond to a valid position in the bitset. Parameters pos - position of the bit to return (counting from 0) Return value true if the requested bit is set, false otherwise. Exceptions std::out_of_range if pos does not correspond to a valid position within the bitset. Example // Run this code #include <bit> #include <bitset> #include <cassert> #include <iostream> #include <stdexcept> int main() { std::bitset<10> b1("1111010000"); std::size_t idx = 0; while (idx < b1.size() && !b1.test(idx)) ++idx; assert(static_cast<int>(idx) == std::countr_zero(b1.to_ulong())); if (idx < b1.size()) std::cout << "The first set bit is at index " << idx << '\n'; else std::cout << "no set bits\n"; try { std::bitset<0B10'1001'1010> bad; if (bad.test(bad.size())) std::cout << "Expect unexpected!\n"; } catch (std::out_of_range const& ex) { std::cout << "Exception: " << ex.what() << '\n'; } } Possible output: The first set bit is at index 4 Exception: bitset::test: __position (which is 666) >= _Nb (which is 666) See also operator[] accesses specific bit (public member function) popcount counts the number of 1 bits in an unsigned integer (C++20) (function template) has_single_bit checks if a number is an integral power of 2 (C++20) (function template) http://cppreference.com 2024.06.10 std::bitset::test(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Example | Possible output: | See also
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