fegetround, fesetround - cppreference.com

##### cppreference.com

##### Search

Create account

##### Namespaces

- Page
- Discussion

##### Variants

##### Views

- View
- Edit
- History

##### Actions

# fegetround, fesetround

From cppreference.com
< c‎ | numeric‎ | fenv

Defined in header `<fenv.h>` |  |
int fesetround( int round ); | (1) | (since C99)
int fegetround(); | (2) | (since C99)

1) Attempts to establish the floating-point rounding direction equal to the argument argument `round`, which is expected to be one of the floating point rounding macros.

2) Returns the value of the floating point rounding macro that corresponds to the current rounding direction.

### [edit] Parameters

round | - | rounding direction, one of floating point rounding macros

### [edit] Return value

1) ​0​ on success, non-zero otherwise.

2) the floating point rounding macro describing the current rounding direction or a negative value if the direction cannot be determined.

### [edit] Notes

The current rounding mode, reflecting the effects of the most recent `fesetround`, can also be queried with FLT_ROUNDS.

### [edit] Example

Run this code

    #include <stdio.h>
    #include <math.h>
    #include <fenv.h>

    #pragma STDC FENV_ACCESS ON
    void show_fe_current_rounding_method(void)
    {
        printf("current rounding method:  ");
        switch (fegetround()) {
               case FE_TONEAREST:  printf ("FE_TONEAREST");  break;
               case FE_DOWNWARD:   printf ("FE_DOWNWARD");   break;
               case FE_UPWARD:     printf ("FE_UPWARD");     break;
               case FE_TOWARDZERO: printf ("FE_TOWARDZERO"); break;
               default:            printf ("unknown");
        };
        printf("\n");
    }

    int main(void)
    {
        /* Default rounding method */
        show_fe_current_rounding_method();
        printf("+11.5 -> %+4.1f\n", rint(+11.5)); /* midway between two integers */
        printf("+12.5 -> %+4.1f\n", rint(+12.5)); /* midway between two integers */

        /* Save current rounding method. */
        int curr_method = fegetround();

        /* Temporarily change current rounding method. */
        fesetround(FE_DOWNWARD);
        show_fe_current_rounding_method();
        printf("+11.5 -> %+4.1f\n", rint(+11.5));
        printf("+12.5 -> %+4.1f\n", rint(+12.5));

        /* Restore default rounding method. */
        fesetround(curr_method);
        show_fe_current_rounding_method();

        return 0;
    }

Possible output:

    current rounding method:  FE_TONEAREST
    +11.5 -> +12.0
    +12.5 -> +12.0
    current rounding method:  FE_DOWNWARD
    +11.5 -> +11.0
    +12.5 -> +12.0
    current rounding method:  FE_TONEAREST

### [edit] References

- C11 standard (ISO/IEC 9899:2011):

  - 7.6.3.1 The fegetround function (p: 212)

  - 7.6.3.2 The fesetround function (p: 212-213)

- C99 standard (ISO/IEC 9899:1999):

  - 7.6.3.1 The fegetround function (p: 193)

  - 7.6.3.2 The fesetround function (p: 193-194)

### [edit] See also

nearbyintnearbyintfnearbyintl (C99)(C99)(C99) | rounds to an integer using current rounding mode (function) [edit]
rintrintfrintllrintlrintflrintlllrintllrintfllrintl (C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99) | rounds to an integer using current rounding mode with exception if the result differs (function) [edit]
C++ documentation for fegetround, fesetround

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=c/numeric/fenv/feround&oldid=77242"