std::bitset::test - cppreference.com (original) (raw)

| | (constexpr since C++23) | | -------------------------- |

Returns the value of the bit at the position pos (counting from 0).

Unlike operator[], it performs a bounds check.

[edit] Parameters

[edit] Return value

true if the requested bit is set, false otherwise.

[edit] Exceptions

Throws std::out_of_range if pos does not correspond to a valid bit position.

[edit] Example

#include #include #include #include #include   int main() { std::bitset<10> b1("1111010000");   std::size_t idx = 0; while (idx < b1.size() && !b1.test(idx)) ++idx;   assert(static_cast(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)

[edit] Defect reports

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

[edit] See also

| | accesses specific bit (public member function) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | counts the number of 1 bits in an unsigned integer (function template) [edit] | | | checks if a number is an integral power of 2 (function template) [edit] |