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std::signbit

From cppreference.com
< cpp‎ | numeric‎ | math
 
 
 
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signbit
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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).

Contents

[edit] Parameters

arg - floating point value

[edit] Return value

true if arg is negative, false otherwise

[edit] Notes

This function detects the sign bit of zeroes, infinities, and NaNs. Along with std::copysign, std::signbit is one of the only two portable ways to examine the sign of a NaN.

[edit] 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

[edit] See also

absolute value of a floating point value (|x|)
(function) [edit]
(C++11)
copies the sign of a floating point value
(function) [edit]
C documentation for signbit