fdim, fdimf, fdiml

 

C

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Concurrency support(C11)

Technical Specifications

Symbol index

 

Numerics

Common mathematical functions

Floating-point environment(C99)

Pseudo-random number generation

Complex number arithmetic(C99)

Type-generic math(C99)

Bit manipulation(C23)

Checked integer arithmetic(C23)

 

Common mathematical functions

Functions Basic operations abslabsllabsimaxabs (C99)(C99) fabs divldivlldivimaxdiv (C99)(C99) fmod remainder (C99) remquo (C99) fma (C99) fdim (C99) nannanfnanlnandN (C99)(C99)(C99)(C23) Maximum/minimum operations fmax (C99) fmin (C99) fmaximum (C23) fminimum (C23) fmaximum_mag (C23)  fmaximum_num (C23) fminimum_mag (C23) fminimum_num (C23) fmaximum_mag_num (C23) fminimum_mag_num (C23)   Exponential functions exp exp10 (C23) exp2 (C99) expm1 (C99) exp10m1 (C23) exp2m1 (C23) log log10 log2 (C99) log1plogp1 (C99)(C23) log10p1 (C23) log2p1 (C23) Power functions sqrt cbrt (C99) rootn (C23) rsqrt (C23) hypot (C99) compound (C23) pow pown (C23) powr (C23) Trigonometric and hyperbolic functions sin cos tan asin acos atan atan2 sinpi (C23) cospi (C23) tanpi (C23) asinpi (C23) acospi (C23) atanpi (C23) atan2pi (C23) sinh cosh tanh asinh (C99) acosh (C99) atanh (C99)

Nearest integer floating-point ceil floor roundlroundllround (C99)(C99)(C99) roundeven (C23) trunc (C99) nearbyint (C99) rintlrintllrint (C99)(C99)(C99) fromfpfromfpxufromfpufromfpx (C23)(C23)(C23)(C23) Floating-point manipulation ldexp frexp scalbnscalbln (C99)(C99) ilogbllogb (C99)(C23) logb (C99) modf nextafternexttoward (C99)(C99) nextupnextdown (C23)(C23) copysign (C99) canonicalize (C23) Narrowing operations fadd (C23) fsub (C23) fmul (C23) fdiv (C23) ffma (C23) fsqrt (C23) Quantum and quantum exponent quantizedN (C23) quantumdN (C23) samequantumdN (C23) llquantexpdN (C23) Decimal re-encoding functions encodedecdN (C23) decodedecdN (C23) encodebindN (C23) decodebindN (C23) Total order and payload functions totalorder (C23) getpayload (C23) setpayload (C23) setpayloadsig (C23) Classification fpclassify (C99) iscanonical (C23)  isfinite (C99) isinf (C99) isnan (C99) isnormal (C99) signbit (C99) issubnormal (C23) iszero (C23) isgreater (C99) isgreaterequal (C99)   isless (C99) islessequal (C99) islessgreater (C99) isunordered (C99) issignaling (C23) iseqsig (C23)

Error and gamma functions erf (C99) erfc (C99) lgamma (C99) tgamma (C99) Types div_tldiv_tlldiv_timaxdiv_t (C99)(C99) float_tdouble_t (C99)(C99) _Decimal32_t_Decimal64_t (C23)(C23) Macro constants Special floating-point values HUGE_VALHUGE_VALFHUGE_VALLHUGE_VALDN (C99)(C99)(C23) INFINITYDEC_INFINITY (C99)(C23) NANDEC_NAN (C99)(C23) Arguments and return values FP_ILOGB0FP_ILOGBNAN (C99)(C99) FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN (C99)(C99)(C99)(C99)(C99) FP_LLOGB0FP_LLOGBNAN (C23)(C23) FP_INT_UPWARDFP_INT_DOWNWARDFP_INT_TOWARDZEROFP_INT_TONEARESTFROMZEROFP_INT_TONEAREST (C23)(C23)(C23)(C23)(C23) Error handling MATH_ERRNOMATH_ERRNOEXCEPT (C99)(C99)  math_errhandling (C99) Fast operation indicators FP_FAST_FMAFFP_FAST_FMA (C99)(C99) FP_FAST_FADDFP_FAST_FADDLFP_FAST_DADDLFP_FAST_DMADDDN (C23)(C23)(C23)(C23) FP_FAST_FMULFP_FAST_FMULLFP_FAST_DMULLFP_FAST_DMMULDN (C23)(C23)(C23)(C23) FP_FAST_FFMAFP_FAST_FFMALFP_FAST_DFMALFP_FAST_DMFMADN (C23)(C23)(C23)(C23) FP_FAST_FMALFP_FAST_FMADN (C99)(C23) FP_FAST_FSUBFP_FAST_FSUBLFP_FAST_DSUBLFP_FAST_DMSUBDN (C23)(C23)(C23)(C23) FP_FAST_FDIVFP_FAST_FDIVLFP_FAST_DDIVLFP_FAST_DMDIVDN (C23)(C23)(C23)(C23) FP_FAST_FSQRTFP_FAST_FSQRTLFP_FAST_DSQRTLFP_FAST_DMSQRTDN (C23)(C23)(C23)(C23)

 

Defined in header <math.h>
float       fdimf(float x, float y );	(1)	(since C99)
double      fdim(double x, double y );	(2)	(since C99)
longdouble fdiml(longdouble x, longdouble y );	(3)	(since C99)
Defined in header <tgmath.h>
#define fdim( x, y )	(4)	(since C99)

1-3) Returns the positive difference between x and y, that is, if x>y, returns x-y, otherwise (if x≤y), returns +0.

4) Type-generic macro: If any argument has type longdouble, fdiml is called. Otherwise, if any argument has integer type or has type double, fdim is called. Otherwise, fdimf is called.

Parameters

x, y

-

floating-point value

Return value

If successful, returns the positive difference between x and y.

If a range error due to overflow occurs, +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL is returned.

If a range error due to underflow occurs, the correct value (after rounding) is returned.

Error handling

Errors are reported as specified in Template:rllpt.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• If either argument is NaN, NaN is returned.

Notes

Equivalent to fmax(x-y, 0) except for the NaN handling requirements.

Example

Run this code

#include <errno.h>#include <fenv.h>#include <math.h>#include <stdio.h>// #pragma STDC FENV_ACCESS ON   int main(void){printf("fdim(4, 1) = %f, fdim(1, 4)=%f\n", fdim(4,1), fdim(1,4));printf("fdim(4,-1) = %f, fdim(1,-4)=%f\n", fdim(4,-1), fdim(1,-4));//error handlingerrno=0;feclearexcept(FE_ALL_EXCEPT);printf("fdim(1e308, -1e308) = %f\n", fdim(1e308, -1e308));if(errno==ERANGE)perror(" errno == ERANGE");if(fetestexcept(FE_OVERFLOW))puts(" FE_OVERFLOW raised");}

Possible output:

fdim(4, 1) = 3.000000, fdim(1, 4)=0.000000 fdim(4,-1) = 5.000000, fdim(1,-4)=5.000000 fdim(1e308, -1e308) = inf errno == ERANGE: Numerical result out of range FE_OVERFLOW raised

References

• C23 standard (ISO/IEC 9899:2024):

• 7.12.12.1 The fdim functions (p: TBD)

• 7.25 Type-generic math <tgmath.h> (p: TBD)

• F.10.9.1 The fdim functions (p: TBD)

• C17 standard (ISO/IEC 9899:2018):

• 7.12.12.1 The fdim functions (p: 187-188)

• 7.25 Type-generic math <tgmath.h> (p: 272-273)

• F.10.9.1 The fdim functions (p: 386)

• C11 standard (ISO/IEC 9899:2011):

• 7.12.12.1 The fdim functions (p: 257)

• 7.25 Type-generic math <tgmath.h> (p: 373-375)

• F.10.9.1 The fdim functions (p: 530)

• C99 standard (ISO/IEC 9899:1999):

• 7.12.12.1 The fdim functions (p: 238)

• 7.22 Type-generic math <tgmath.h> (p: 335-337)

• F.9.9.1 The fdim functions (p: 466)

See also

abslabsllabs (C99)	computes absolute value of an integral value (\(\small{|x|}\)|x|) (function)
fmaxfmaxffmaxl (C99)(C99)(C99)	determines larger of two floating-point values (function)
C++ documentation for fdim