| Defined in header <cmath> | ||
|---|---|---|
bool signbit( float arg ); | (1) | (since C++11) |
bool signbit( double arg ); | (2) | (since C++11) |
bool signbit( long double arg ); | (3) | (since C++11) |
bool signbit( Integral arg ); | (4) | (since C++11) |
1-3) Determines if the given floating point number
arg is negative. 4) A set of overloads or a function template accepting the
from argument of any integral type. Equivalent to (2) (the argument is cast to double). Parameters
| arg | - | floating point value |
Return value
true if arg is negative, false otherwise.
Notes
This function detects the sign bit of zeroes, infinities, and NaNs. Along with std::copysign, this macro is one of the only two portable ways to examine the sign of a NaN.
Examples
#include <iostream>
#include <cmath>
int main()
{
std::cout << std::boolalpha
<< "signbit(+0.0) = " << std::signbit(+0.0) << '\n'
<< "signbit(-0.0) = " << std::signbit(-0.0) << '\n';
}Output:
signbit(+0.0) = false signbit(-0.0) = true
See also
| absolute value of a floating point value (|x|) (function) | |
| (C++11) | copies the sign of a floating point value (function) |
C documentation for signbit | |
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