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 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.
| round | - | rounding direction, one of floating-point rounding macros |
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.
The current rounding mode, reflecting the effects of the most recent fesetround, can also be queried with FLT_ROUNDS.
#include <fenv.h>
#include <math.h>
#include <stdio.h>
// #pragma STDC FENV_ACCESS ON
void show_fe_current_rounding_direction(void)
{
printf("current rounding direction: ");
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 direction */
show_fe_current_rounding_direction();
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 direction. */
int curr_direction = fegetround();
/* Temporarily change current rounding direction. */
fesetround(FE_DOWNWARD);
show_fe_current_rounding_direction();
printf("+11.5 -> %+4.1f\n", rint(+11.5));
printf("+12.5 -> %+4.1f\n", rint(+12.5));
/* Restore default rounding direction. */
fesetround(curr_direction);
show_fe_current_rounding_direction();
return 0;
}Possible output:
current rounding direction: FE_TONEAREST +11.5 -> +12.0 +12.5 -> +12.0 current rounding direction: FE_DOWNWARD +11.5 -> +11.0 +12.5 -> +12.0 current rounding direction: FE_TONEAREST
|
(C99)(C99)(C99) | rounds to an integer using current rounding mode (function) |
|
(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99) | rounds to an integer using current rounding mode with exception if the result differs (function) |
C++ documentation for fegetround, fesetround |
|
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