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      fmod, fmodf, fmodl

      From cppreference.com
      <c‎ |numeric‎ |math
       
       
       
      Common mathematical functions
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      fmod
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      Defined in header<math.h>
      float       fmodf(float x,float y);
      		 (1)(since C99)
      double      fmod(double x,double y);
      		 (2)
      longdouble fmodl(longdouble x,longdouble y);
      		 (3)(since C99)
      Defined in header<tgmath.h>
      #define fmod( x, y )
      		 (4)(since C99)
      1-3) Computes the floating-point remainder of the division operationx/ y.
      4) Type-generic macro: If any argument has typelongdouble,fmodl is called. Otherwise, if any argument has integer type or has typedouble,fmod is called. Otherwise,fmodf is called.

      The floating-point remainder of the division operationx/ y calculated by this function is exactly the valuex- n* y, wheren isx/ y with its fractional part truncated.

      The returned value has the same sign asx and is less or equal toy in magnitude.

      Contents

      [edit]Parameters

      x, y - floating-point values

      [edit]Return value

      If successful, returns the floating-point remainder of the divisionx/ y as defined above.

      If a domain error occurs, an implementation-defined value is returned (NaN where supported).

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

      [edit]Error handling

      Errors are reported as specified inmath_errhandling.

      Domain error may occur ify is zero.

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

      • Ifx is ±0 andy is not zero, ±0 is returned.
      • Ifx is ±∞ andy is not NaN, NaN is returned andFE_INVALID is raised.
      • Ify is ±0 andx is not NaN, NaN is returned andFE_INVALID is raised.
      • Ify is ±∞ andx is finite,x is returned.
      • If either argument is NaN, NaN is returned.

      [edit]Notes

      POSIX requires that a domain error occurs ifx is infinite ory is zero.

      fmod, but notremainder is useful for doing silent wrapping of floating-point types to unsigned integer types:(0.0<=(y= fmod(rint(x),65536.0))? y:65536.0+ y) is in the range[-0.0, 65535.0], which corresponds tounsignedshort, butremainder(rint(x),65536.0) is in the range[-32767.0, +32768.0], which is outside of the range ofsignedshort.

      Thedouble version offmod behaves as if implemented as follows:

      double fmod(double x,double y){#pragma STDC FENV_ACCESS ONdouble result=remainder(fabs(x),(y=fabs(y)));if(signbit(result))        result+= y;returncopysign(result, x);}

      [edit]Example

      Run this code
      #include <fenv.h>#include <math.h>#include <stdio.h> // #pragma STDC FENV_ACCESS ON int main(void){printf("fmod(+5.1, +3.0) = %.1f\n", fmod(5.1,3));printf("fmod(-5.1, +3.0) = %.1f\n", fmod(-5.1,3));printf("fmod(+5.1, -3.0) = %.1f\n", fmod(5.1,-3));printf("fmod(-5.1, -3.0) = %.1f\n", fmod(-5.1,-3)); // special valuesprintf("fmod(+0.0, 1.0) = %.1f\n", fmod(0,1));printf("fmod(-0.0, 1.0) = %.1f\n", fmod(-0.0,1));printf("fmod(+5.1, Inf) = %.1f\n", fmod(5.1, INFINITY)); // error handlingfeclearexcept(FE_ALL_EXCEPT);printf("fmod(+5.1, 0) = %.1f\n", fmod(5.1,0));if(fetestexcept(FE_INVALID))puts("    FE_INVALID raised");}

      Possible output:

      fmod(+5.1, +3.0) = 2.1fmod(-5.1, +3.0) = -2.1fmod(+5.1, -3.0) = 2.1fmod(-5.1, -3.0) = -2.1fmod(+0.0, 1.0) = 0.0fmod(-0.0, 1.0) = -0.0fmod(+5.1, Inf) = 5.1fmod(+5.1, 0) = nan    FE_INVALID raised

      [edit]References

      • C23 standard (ISO/IEC 9899:2024):
      • 7.12.10.1 The fmod functions (p: TBD)
      • 7.25 Type-generic math <tgmath.h> (p: TBD)
      • F.10.7.1 The fmod functions (p: TBD)
      • C17 standard (ISO/IEC 9899:2018):
      • 7.12.10.1 The fmod functions (p: 185)
      • 7.25 Type-generic math <tgmath.h> (p: 274-275)
      • F.10.7.1 The fmod functions (p: 385)
      • C11 standard (ISO/IEC 9899:2011):
      • 7.12.10.1 The fmod functions (p: 254)
      • 7.25 Type-generic math <tgmath.h> (p: 373-375)
      • F.10.7.1 The fmod functions (p: 528)
      • C99 standard (ISO/IEC 9899:1999):
      • 7.12.10.1 The fmod functions (p: 235)
      • 7.22 Type-generic math <tgmath.h> (p: 335-337)
      • F.9.7.1 The fmod functions (p: 465)
      • C89/C90 standard (ISO/IEC 9899:1990):
      • 4.5.6.4 The fmod function

      [edit]See also

      computes quotient and remainder of integer division
      (function)[edit]
      computes signed remainder of the floating-point division operation
      (function)[edit]
      (C99)(C99)(C99)
      		 computes signed remainder as well as the three last bits of the division operation
      (function)[edit]
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