std::bitset<N>::test
bool test( std::size_t pos ) const; |
Returns the value of the bit at the position pos.
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 |
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
#include <iostream>
#include <bitset>
#include <bit>
#include <cassert>
#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 {
if (b1.test(b1.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 10) >= _Nb (which is 10)
See also
| 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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