<cmath> (math.h)

function
<cmath> <ctgmath>

lrint

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

See llrint for an equivalent function that returns a long 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 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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
/* lrint example */
#include <stdio.h>      /* printf */
#include <fenv.h>       /* fegetround, FE_* */
#include <math.h>       /* lrint */

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


Possible output:

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

See also