rint

rint

Rounds a floating-point number to an integer value

#include <math.h>
double rint ( double x  );
float rintf ( float x  );
long double rintl ( long double x  );

The rint( ) functions round a floating-point number to the next integer value in the current rounding direction. The current rounding direction is an attribute of the floating-point environment that you can read and modify using the fegetround( ) and fesetround( ) functions. The rint( ) functions are similar to the nearbyint( ) functions, except that the rint( ) functions may raise the FE_INEXACT exception (depending on the implementation) when the result of the rounding is different from the argument.

Example

struct round_modes { int id; char *str; }  arrModes[ ] =
{
  #ifdef FE_TONEAREST
   { FE_TONEAREST, "FE_TONEAREST: round to nearest representable value" },
  #endif
  #ifdef FE_DOWNWARD
   { FE_DOWNWARD, "FE_DOWNWARD: round toward -Inf" },
  #endif
  #ifdef FE_UPWARD
   { FE_UPWARD, "FE_UPWARD: round toward +Inf" },
  #endif
  #ifdef FE_TOWARDZERO
   { FE_TOWARDZERO, "FE_TOWARDZERO: round toward 0" }
  #endif
};

int nModes = sizeof( arrModes) / sizeof(*arrModes);

 #pragma STDC FENV_ACCESS ON

for ( int i = 0; i < nModes; ++i)
{
  if ( fesetround( arrModes[i].id) != 0)
    break;
  printf( "Current rounding mode: %s\n", arrModes[i].str );

  printf( "rint(1.4)  = %4.1f    rint(1.5)  = %4.1f\n",
          rint(1.4), rint(1.5) );
  printf( "rint(-1.4) = %4.1f    rint(-1.5) = %4.1f\n",
          rint(-1.4), rint(-1.5) );
}

If the implementation supports all four rounding modes, this code produces the following output:

Current rounding mode: FE_TONEAREST: round to nearest representable value
rint(1.4)  =  1.0    rint(1.5)  =  2.0
rint(-1.4) = -1.0    rint(-1.5) = -2.0
Current rounding mode: FE_DOWNWARD: round toward -Inf
rint(1.4)  =  1.0    rint(1.5)  =  1.0
rint(-1.4) = -2.0    rint(-1.5) = -2.0
Current rounding mode: FE_UPWARD: round toward +Inf
rint(1.4)  =  2.0    rint(1.5)  =  2.0
rint(-1.4) = -1.0    rint(-1.5) = -1.0
Current rounding mode: FE_TOWARDZERO: round toward 0
rint(1.4)  =  1.0    rint(1.5)  =  1.0
rint(-1.4) = -1.0    rint(-1.5) = -1.0

Example

See Also