floor

 

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Common mathematical functions

Functions
Basic operations
abslabsllabsimaxabs (C99) fabs divldivlldivimaxdiv (C99) fmod	remainder (C99) remquo (C99) fma (C99) fmax (C99) fmin (C99) fdim (C99) nannanfnanl (C99)(C99)(C99)
Exponential functions
exp exp2 (C99) expm1 (C99)	log log10 log1p (C99) log2 (C99)
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sqrt cbrt (C99)	hypot (C99) pow
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sin cos tan asin acos atan atan2	sinh cosh tanh asinh (C99) acosh (C99) atanh (C99)
Error and gamma functions
erf (C99) erfc (C99)	lgamma (C99) tgamma (C99)
Nearest integer floating point operations
ceil floor roundlroundllround (C99)(C99)(C99)	trunc (C99) nearbyint (C99) rintlrintllrint (C99)(C99)(C99)
Floating point manipulation functions
ldexp scalbnscalbln (C99)(C99) ilogb (C99) logb (C99)	frexp modf nextafternexttoward (C99)(C99) copysign (C99)
Classification
fpclassify (C99)
isfinite (C99)
isinf (C99)
isnan (C99)
isnormal (C99)
signbit (C99)
Macro constants
HUGE_VALFHUGE_VALHUGE_VALL (C99)(C99)	FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN (C99)(C99)(C99)(C99)(C99)

 

Defined in header <math.h>
float       floorf( float arg );		(since C99)
double      floor( double arg );
long double floorl( long double arg );		(since C99)

Computes nearest integer not greater than arg.

Parameters

arg

-

floating point value

Return value

Nearest integer not greater than arg

Notes

The integer value can be always represented by the given floating point type.

Example

Run this code

#include <stdio.h>
#include <math.h>
#include <errno.h>
#include <fenv.h>
#include <string.h>
 
#pragma STDC FENV_ACCESS ON
 
void show_fe_exceptions(void)
{
    printf("current exceptions raised: ");
    if(fetestexcept(FE_DIVBYZERO))     printf(" FE_DIVBYZERO");
    if(fetestexcept(FE_INEXACT))       printf(" FE_INEXACT");
    if(fetestexcept(FE_INVALID))       printf(" FE_INVALID");
    if(fetestexcept(FE_OVERFLOW))      printf(" FE_OVERFLOW");
    if(fetestexcept(FE_UNDERFLOW))     printf(" FE_UNDERFLOW");
    if(fetestexcept(FE_ALL_EXCEPT)==0) printf(" none");
    printf("\n");
}
 
int main(void)
{
    printf("floor(+2.4)      = %+.1f\n", floor(+2.4));
    printf("floor(-2.4)      = %+.1f\n", floor(-2.4));
    printf("floor(+0.0)      = %+.1f\n", floor(+0.0));
    printf("floor(-0.0)      = %+.1f\n", floor(-0.0));
    printf("floor(+INFINITY) = %+f\n",   floor(+INFINITY));
    printf("floor(-INFINITY) = %+f\n",   floor(-INFINITY));
    printf("floor(NAN)       = %f\n",    floor(NAN));
    printf("\n");
 
    /* no "inexact" floating-point exception for finite non-integer arguments */
    errno = 0; feclearexcept(FE_ALL_EXCEPT);
    printf("floor(2.4)       = %.1f\n", floor(2.4));
    printf("%s\n",strerror(errno));
    show_fe_exceptions();
 
    return 0;
}

Possible output:

floor(+2.4)      = +2.0
floor(-2.4)      = -3.0
floor(+0.0)      = +0.0
floor(-0.0)      = -0.0
floor(+INFINITY) = +inf
floor(-INFINITY) = -inf
floor(NAN)       = nan
 
floor(2.4)       = 2.0
Success
current exceptions raised:  none

See also

ceilceilfceill (C99)(C99)	computes smallest integer not less than the given value (function)
trunctruncftruncl (C99)(C99)(C99)	rounds to nearest integer not greater in magnitude than the given value (function)
roundlroundllround (C99)(C99)(C99)	rounds to nearest integer, rounding away from zero in halfway cases (function)
C++ documentation for floor