NAME [Toc] [Back]
fenv - floating-point environment macros and functions
SYNOPSIS [Toc] [Back]
DESCRIPTION [Toc] [Back]
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 Itanium(R)-based systems the
control modes include the rounding direction mode, the gradual/flushto-zero
underflow mode, and the trap enables.
The following types are defined:
fenv_t Represents the entire floating-point
fexcept_t Represents the floating-point exception flags
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
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
FE_TONEAREST The round-to-nearest rounding direction mode.
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FE_UPWARD The round-toward-positive-infinity rounding
FE_DOWNWARD The round-toward-negative-infinity rounding
FE_TOWARDZERO The round-toward-zero rounding direction
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: fegetflushtozero(), fesetflushtozero(),
fegettrapenable(), and fesettrapenable().
FILES [Toc] [Back]
SEE ALSO [Toc] [Back]
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),
STANDARDS CONFORMANCE [Toc] [Back]
<fenv.h> : ISO/IEC C99 (including Annex F, "IEC 60559 floating-point
Hewlett-Packard Company - 2 - HP-UX 11i Version 2: August 2003 [ Back ]