C++

Reference

<cmath> (math.h)

function
<cmath> <ctgmath>

llrint

long long int llrint  (double x);long long int llrintf (float x);long long int llrintl (long double x);
long long int llrint (double x);long long int llrint (float x);long long int llrint (long double x);long long int llrint (T x);           // additional overloads for integral types
Round and cast to long long integer
Rounds x to an integral value, using the rounding direction specified by fegetround, and returns it as a value of type long long int.

See lrint for an equivalent function that returns a long int.

Header <tgmath.h> provides a type-generic macro version of this function.
Additional overloads are provided in this header (<cmath>) for the integral types: These overloads effectively cast x to a double before calculations (defined for T being any integral type).

Parameters

x
Value to round.

Return Value

The value of x rounded to a nearby integral, casted to a value of type long long int.
If the rounded value is outside the range of the return type, the value returned is unspecified, and a domain error or an overflow range error may occur (or none, depending on implementation).

If a domain error occurs:
- And math_errhandling has MATH_ERRNO set: the global variable errno is set to EDOM.
- And math_errhandling has MATH_ERREXCEPT set: FE_INVALID is raised.

If an overflow range error occurs:
- And math_errhandling has MATH_ERRNO set: the global variable errno is set to ERANGE.
- And math_errhandling has MATH_ERREXCEPT set: FE_OVERFLOW is raised.

Example

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/* llrint example */
#include <stdio.h>      /* printf */
#include <fenv.h>       /* fegetround, FE_* */
#include <math.h>       /* llrint */

int main ()
{
  printf ("rounding using ");
  switch (fegetround()) {
    case FE_DOWNWARD: printf ("downward"); break;
    case FE_TONEAREST: printf ("to-nearest"); break;
    case FE_TOWARDZERO: printf ("toward-zero"); break;
    case FE_UPWARD: printf ("upward"); break;
    default: printf ("unknown");
  }
  printf (" rounding:\n");

  printf ( "llrint (2.3) = %lld\n", llrint(2.3) );
  printf ( "llrint (3.8) = %lld\n", llrint(3.8) );
  printf ( "llrint (-2.3) = %lld\n", llrint(-2.3) );
  printf ( "llrint (-3.8) = %lld\n", llrint(-3.8) );
  return 0;
}

Possible output:

Rounding using to-nearest rounding:
llrint (2.3) = 2
llrint (3.8) = 4
llrint (-2.3) = -2
llrint (-3.8) = -4


See also

nearbyint
Round to nearby integral value (function)
rint
Round to integral value (function)
lrint
Round and cast to long integer (function)
round
Round to nearest (function)
floor
Round down value (function)
ceil
Round up value (function)
trunc
Truncate value (function)