Checking a bit

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Example

C-style bit-manipulation

The value of the bit can be obtained by shifting the number to the right x times and then performing bitwise AND (&) on it:

(number >> x) & 1LL;  // 1 if the 'x'th bit of 'number' is set, 0 otherwise

The right-shift operation may be implemented as either an arithmetic (signed) shift or a logical (unsigned) shift. If number in the expression number >> x has a signed type and a negative value, the resulting value is implementation-defined.

If we need the value of that bit directly in-place, we could instead left shift the mask:

(number & (1LL << x));  // (1 << x) if the 'x'th bit of 'number' is set, 0 otherwise

Either can be used as a conditional, since all non-zero values are considered true.

Using std::bitset

std::bitset<4> num(std::string("0010"));
bool bit_val = num.test(1);  // bit_val value is set to true;

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Contributors: 5
2016-11-18
Licensed under: CC-BY-SA

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