fegetenv, fesetenv
From cppreference.com
C
Concurrency support (C11)
Floating-point environment
Functions
(C99)
(C99)
(C99)
(C99)(C99)
(C99)(C99)
fegetenvfesetenv
(C99)
(C99)
(C99)
Macro constants
(C99)
Defined in header
<fenv.h>
int fegetenv( fenv_t* envp );
(1)
(since C99)
int fesetenv( const fenv_t* envp );
(2)
(since C99)
1) Attempts to store the status of the floating-point environment in the object pointed to by envp.
2) Attempts to establish the floating-point environment from the object pointed to by envp. The value of that object must be previously obtained by a call to feholdexcept or fegetenv or be a floating-point macro constant. If any of the floating-point status flags are set in envp, they become set in the environment (and are then testable with fetestexcept ), but the corresponding floating-point exceptions are not raised (execution continues uninterrupted)
[edit] Parameters
envp
-
pointer to the object of type fenv_t which holds the status of the floating-point environment
[edit] Return value
0 on success, non-zero otherwise.
[edit] Example
Run this code
#include <stdio.h> #include <math.h> #include <fenv.h> #pragma STDC FENV_ACCESS ON void show_fe_exceptions(void) { printf ("current exceptions raised: "); if(fetestexcept (FE_DIVBYZERO )) printf (" FE_DIVBYZERO"); if(fetestexcept (FE_INEXACT )) printf (" FE_INEXACT"); if(fetestexcept (FE_INVALID )) printf (" FE_INVALID"); if(fetestexcept (FE_OVERFLOW )) printf (" FE_OVERFLOW"); if(fetestexcept (FE_UNDERFLOW )) printf (" FE_UNDERFLOW"); if(fetestexcept (FE_ALL_EXCEPT )==0) printf (" none"); printf ("\n"); } void show_fe_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"); } void show_fe_environment(void) { show_fe_exceptions(); show_fe_rounding_method(); } int main(void) { fenv_t curr_env; int rtn; /* Show default environment. */ show_fe_environment(); printf ("\n"); /* Perform some computation under default environment. */ 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 */ show_fe_environment(); printf ("\n"); /* Save current environment. */ rtn = fegetenv(&curr_env); /* Perform some computation with new rounding method. */ feclearexcept (FE_ALL_EXCEPT ); fesetround (FE_DOWNWARD ); printf ("1.0/0.0 = %f\n", 1.0/0.0); printf ("+11.5 -> %+4.1f\n", rint (+11.5)); printf ("+12.5 -> %+4.1f\n", rint (+12.5)); show_fe_environment(); printf ("\n"); /* Restore previous environment. */ rtn = fesetenv(&curr_env); show_fe_environment(); return 0; }
Output:
current exceptions raised: none current rounding method: FE_TONEAREST +11.5 -> +12.0 +12.5 -> +12.0 current exceptions raised: FE_INEXACT current rounding method: FE_TONEAREST 1.0/0.0 = inf +11.5 -> +11.0 +12.5 -> +12.0 current exceptions raised: FE_DIVBYZERO FE_INEXACT current rounding method: FE_DOWNWARD current exceptions raised: FE_INEXACT current rounding method: FE_TONEAREST
[edit] References
- C11 standard (ISO/IEC 9899:2011):
- 7.6.4.1 The fegetenv function (p: 213)
- 7.6.4.3 The fesetenv function (p: 214)
- C99 standard (ISO/IEC 9899:1999):
- 7.6.4.1 The fegetenv function (p: 194)
- 7.6.4.3 The fesetenv function (p: 195)
[edit] See also
(C99)
(function) [edit]
(C99)
(function) [edit]
C++ documentation for fegetenv, fesetenv