bool test( std::size_t pos ) const; | (until C++23) | |
constexpr bool test( std::size_t pos ) const; | (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.
| pos | - | position of the bit to return (counting from 0) |
true if the requested bit is set, false otherwise.
std::out_of_range if pos does not correspond to a valid position within the bitset.
#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 << "first set bit 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:
first set bit at index 4 Exception: bitset::test: __position (which is 666) >= _Nb (which is 666)
| accesses specific bit (public member function) |
|
|
(C++20) | counts the number of 1 bits in an unsigned integer (function template) |
|
(C++20) | checks if a number is an integral power of two (function template) |
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