signbit

Types

div_tldiv_tlldiv_timaxdiv_t (哋它亢99)(哋它亢99)

float_tdouble_t (哋它亢99)(哋它亢99)
_Decimal32_t_Decimal64_t (哋它亢23)(哋它亢23)

Functions

Basic operations

abslabsllabsimaxabs (哋它亢99)(哋它亢99)
fabs
divldivlldivimaxdiv (哋它亢99)(哋它亢99)

fmod
remainder (哋它亢99)
remquo (哋它亢99)
fma (哋它亢99)
fdim (哋它亢99)
nannanfnanlnandN (哋它亢99)(哋它亢99)(哋它亢99)(哋它亢23)

Maximum/minimum operations

fmax (哋它亢99)
fmaximum (哋它亢23)
fmaximum_mag (哋它亢23)
fmaximum_num (哋它亢23)
fmaximum_mag_num (哋它亢23)

fmin (哋它亢99)
fminimum (哋它亢23)
fminimum_mag (哋它亢23)
fminimum_num (哋它亢23)
fminimum_mag_num (哋它亢23)

Exponential functions

exp
exp10 (哋它亢23)
exp2 (哋它亢99)
expm1 (哋它亢99)
exp10m1 (哋它亢23)
exp2m1 (哋它亢23)

log
log10
log2 (哋它亢99)
log1plogp1 (哋它亢99)(哋它亢23)
log10p1 (哋它亢23)
log2p1 (哋它亢23)

Power functions

sqrt
cbrt (哋它亢99)
rootn (哋它亢23)
rsqrt (哋它亢23)

hypot (哋它亢99)
compound (哋它亢23)
pow
pown (哋它亢23)
powr (哋它亢23)

Trigonometric and hyperbolic functions

sin
cos
tan
asin
acos
atan
atan2
sinpi (哋它亢23)
cospi (哋它亢23)
tanpi (哋它亢23)

asinpi (哋它亢23)
acospi (哋它亢23)
atanpi (哋它亢23)
atan2pi (哋它亢23)
sinh
cosh
tanh
asinh (哋它亢99)
acosh (哋它亢99)
atanh (哋它亢99)

Error and gamma functions

erf (哋它亢99)
erfc (哋它亢99)

lgamma (哋它亢99)
tgamma (哋它亢99)

Nearest integer floating-point operations

ceil
floor
roundlroundllround (哋它亢99)(哋它亢99)(哋它亢99)
roundeven (哋它亢23)
trunc (哋它亢99)

nearbyint (哋它亢99)
rintlrintllrint (哋它亢99)(哋它亢99)(哋它亢99)
fromfpfromfpxufromfpufromfpx (哋它亢23)(哋它亢23)(哋它亢23)(哋它亢23)

Floating-point manipulation functions

ldexp
frexp
scalbnscalbln (哋它亢99)(哋它亢99)
ilogbllogb (哋它亢99)(哋它亢23)
logb (哋它亢99)

modf
nextafternexttoward (哋它亢99)(哋它亢99)
nextupnextdown (哋它亢23)(哋它亢23)
copysign (哋它亢99)
canonicalize (哋它亢23)

Narrowing operations

fadd (哋它亢23)
fsub (哋它亢23)
fmul (哋它亢23)

fdiv (哋它亢23)
ffma (哋它亢23)
fsqrt (哋它亢23)

Quantum and quantum exponent functions

quantizedN (哋它亢23)
samequantumdN (哋它亢23)

quantumdN (哋它亢23)
llquantexpdN (哋它亢23)

Decimal re-encoding functions

encodedecdN (哋它亢23)
decodedecdN (哋它亢23)

encodebindN (哋它亢23)
decodebindN (哋它亢23)

Total order and payload functions

totalorder (哋它亢23)
getpayload (哋它亢23)

setpayload (哋它亢23)
setpayloadsig (哋它亢23)

Classification

fpclassify (哋它亢99)
iscanonical (哋它亢23)
isfinite (哋它亢99)
isinf (哋它亢99)
isnan (哋它亢99)
isnormal (哋它亢99)
signbit (哋它亢99)
issubnormal (哋它亢23)
iszero (哋它亢23)

isgreater (哋它亢99)
isgreaterequal (哋它亢99)
isless (哋它亢99)
islessequal (哋它亢99)
islessgreater (哋它亢99)
isunordered (哋它亢99)
issignaling (哋它亢23)
iseqsig (哋它亢23)

Macro constants

Special floating-point values

HUGE_VALFHUGE_VALHUGE_VALLHUGE_VALDN

(哋它亢99)(哋它亢99)(哋它亢23)

INFINITYDEC_INFINITY (哋它亢99)(哋它亢23)
NANDEC_NAN (哋它亢99)(哋它亢23)

Arguments and return values

FP_ILOGB0FP_ILOGBNAN (哋它亢99)(哋它亢99)
FP_INT_UPWARDFP_INT_DOWNWARDFP_INT_TOWARDZEROFP_INT_TONEARESTFROMZEROFP_INT_TONEAREST (哋它亢23)(哋它亢23)(哋它亢23)(哋它亢23)(哋它亢23)

FP_LLOGB0FP_LLOGBNAN (哋它亢23)(哋它亢23)
FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN (哋它亢99)(哋它亢99)(哋它亢99)(哋它亢99)(哋它亢99)

Error handling

MATH_ERRNOMATH_ERRNOEXCEPT

(哋它亢99)(哋它亢99)

math_errhandling (哋它亢99)

Fast operation indicators

FP_FAST_FMAFFP_FAST_FMA (哋它亢99)(哋它亢99)
FP_FAST_FADDFP_FAST_FADDLFP_FAST_DADDLFP_FAST_DMADDDN (哋它亢23)(哋它亢23)(哋它亢23)(哋它亢23)
FP_FAST_FMULFP_FAST_FMULLFP_FAST_DMULLFP_FAST_DMMULDN (哋它亢23)(哋它亢23)(哋它亢23)(哋它亢23)
FP_FAST_FFMAFP_FAST_FFMALFP_FAST_DFMALFP_FAST_DMFMADN (哋它亢23)(哋它亢23)(哋它亢23)(哋它亢23)

FP_FAST_FMALFP_FAST_FMADN (哋它亢99)(哋它亢23)
FP_FAST_FSUBFP_FAST_FSUBLFP_FAST_DSUBLFP_FAST_DMSUBDN (哋它亢23)(哋它亢23)(哋它亢23)(哋它亢23)
FP_FAST_FDIVFP_FAST_FDIVLFP_FAST_DDIVLFP_FAST_DMDIVDN (哋它亢23)(哋它亢23)(哋它亢23)(哋它亢23)
FP_FAST_FSQRTFP_FAST_FSQRTLFP_FAST_DSQRTLFP_FAST_DMSQRTDN (哋它亢23)(哋它亢23)(哋它亢23)(哋它亢23)

Defined in header `<math.h>`
#define signbit( arg ) /* implementation defined */		(since 哋它亢99)

Determines if the given floating-point number arg is negative. The macro returns an integral value.

Parameters

arg

-

floating-point value

Return value

Nonzero integral value if arg is negative, 0 otherwise.

Notes

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

Example

Run this code

#include <math.h>
#include <stdio.h>
 
int main(void)
{
    printf("signbit(+0.0) = %d\n", signbit(+0.0));
    printf("signbit(-0.0) = %d\n", signbit(-0.0));
}

Possible output:

signbit(+0.0) = 0
signbit(-0.0) = 128

References

哋它亢23 standard (ISO/IEC 9899:2023):

7.12.3.6 The signbit macro (p: TBD)

哋它亢17 standard (ISO/IEC 9899:2018):

7.12.3.6 The signbit macro (p: TBD)

哋它亢11 standard (ISO/IEC 9899:2011):

7.12.3.6 The signbit macro (p: 237)

哋它亢99 standard (ISO/IEC 9899:1999):

7.12.3.6 The signbit macro (p: 218)

Language
Headers
Type support
Program utilities
Variadic function support
Error handling
Dynamic memory management
Strings library
Algorithms
Numerics
Date and time utilities
Input/output support
Localization support
Concurrency support (哋它亢11)
Technical Specifications
Symbol index

Common mathematical functions
Floating-point environment (哋它亢99)
Pseudo-random number generation
Complex number arithmetic (哋它亢99)
Type-generic math (哋它亢99)

fabsfabsffabsl (哋它亢99)(哋它亢99)	computes absolute value of a floating-point value (\(\small{\|x\|}\) $\|x\|$ ) (function)
copysigncopysignfcopysignl (哋它亢99)(哋它亢99)(哋它亢99)	produces a value with the magnitude of a given value and the sign of another given value (function)