NAN

 

C

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

 

Numerics

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)

 

Common mathematical functions

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 NAN /*implementation defined*/		(since 哋它亢99)

The macro NAN expands to a constant expression of type float, which evaluates to a quiet not-a-number (QNaN) value. If the implementation does not support QNaNs, this macro constant is not defined.

The style used to print a NaN is implementation-defined.

Notes

There are many different NaN values, differentiated by their payloads and their sign bits. The contents of the payload and the sign bit of the NaN generated by the macro NAN are implementation-defined.

Example

Show style used to print a NaN and IEEE format.

Run this code

#include <inttypes.h>
#include <math.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
 
int main(void)
{
    const double f = NAN;
    uint64_t fn;
    memcpy(&fn, &f, sizeof f);
    printf("NAN:   %f %" PRIx64 "\n", f, fn);
}

Possible output:

NAN:   nan 7ff8000000000000

References

• 哋它亢23 standard (ISO/IEC 9899:2023):

• 7.12/5 NAN (p: TBD)

• F.10/11/13 NAN (p: TBD)

• 哋它亢17 standard (ISO/IEC 9899:2018):

• 7.12/5 NAN (p: TBD)

• F.10/11/13 NAN (p: TBD)

• 哋它亢11 standard (ISO/IEC 9899:2011):

• 7.12/5 NAN (p: 232)

• F.10/11/13 NAN (p: 518)

• 哋它亢99 standard (ISO/IEC 9899:1999):

• 7.12/5 NAN (p: 213)

• F.9/11/13 NAN (p: 455)

See also

nannanfnanl (哋它亢99)(哋它亢99)(哋它亢99)	returns a NaN (not-a-number) (function)
isnan (哋它亢99)	checks if the given number is NaN (function macro)