HP-UX Reference (11i v3 07/02) - 5 Miscellaneous Topics (vol 9)
f
fenv(5) fenv(5)
NAME
fenv - floating-point environment macros and functions
SYNOPSIS
#include <fenv.h>
DESCRIPTION
The header <fenv.h> declares two types and several macros and functions to provide access to the
floating-point environment. The floating-point environment refers collectively to the floating-point status
flags and control modes. A floating-point status flag is a system variable whose value is set (but never
cleared) when a floating-point exception is raised, which occurs as a side effect of exceptional floating-point
arithmetic to provide auxiliary information. A floating-point control mode is a system variable whose value
may be set by the user to affect the subsequent behavior of floating-point arithmetic; on HP 9000 and HP
Integrity servers the control modes include the rounding direction mode, the gradual/flush-to-zero
underflow mode, and the trap enables.
The following types are defined:
fenv_t Represents the entire floating-point environment.
fexcept_t Represents the floating-point exception flags collectively.
The following macros represent the floating-point status flags. They are defined as integral constant
expressions with values such that bitwise ORs of all combinations of the macros result in distinct values.
FE_INEXACT The inexact exception.
FE_DIVBYZERO The division-by-zero exception.
FE_UNDERFLOW The underflow exception.
FE_OVERFLOW The overflow exception.
FE_INVALID The invalid operation exception.
FE_ALL_EXCEPT The bitwise OR of all exception macros.
The following macros represent the rounding direction modes. They are defined as integral constant
expressions with distinct nonnegative values.
FE_TONEAREST The round-to-nearest rounding direction mode.
FE_UPWARD The round-toward-positive-infinity rounding direction mode.
FE_DOWNWARD The round-toward-negative-infinity rounding direction mode.
FE_TOWARDZERO The round-toward-zero rounding direction mode.
The following macro is defined as a pointer to const-qualified fenv_t:
FE_DFL_ENV The default floating-point environment.
To the ISO/IEC C99 specified facilities, the HP implementation adds four HP-specific functions:
feget-
flushtozero()
, fesetflushtozero()
, fegettrapenable(), and
fesettrapenable().
FILES
/usr/include/fenv.h
SEE ALSO
feclearexcept(3M), fegetexceptflag(3M), feraiseexcept(3M), fesetexceptflag(3M), fetestexcept(3M),
fegetround(3M), fesetround(3M), fegetenv(3M), feholdexcept(3M), fesetenv(3M), feupdateenv(3M),
fegetflushtozero(3M), fesetflushtozero(3M), fegettrapenable(3M), fesettrapenable(3M), math(5).
STANDARDS CONFORMANCE
<fenv.h> : ISO/IEC C99 (including Annex F, "IEC 60559 floating-point arithmetic")
172 Hewlett-Packard Company − 1 − HP-UX 11i Version 3: February 2007