fenv(5)                                                             fenv(5)




 NAME    [Toc]    [Back]
      fenv - floating-point environment macros and functions

 SYNOPSIS    [Toc]    [Back]
      #include <fenv.h>

 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
                               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.




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 fenv(5)                                                             fenv(5)




           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: fegetflushtozero(), fesetflushtozero(),
      fegettrapenable(), and fesettrapenable().

 FILES    [Toc]    [Back]
      /usr/include/fenv.h

 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),
      fesettrapenable(3M), math(5).

 STANDARDS CONFORMANCE    [Toc]    [Back]
      <fenv.h> : ISO/IEC C99 (including Annex F, "IEC 60559 floating-point
      arithmetic")


 Hewlett-Packard Company            - 2 -   HP-UX 11i Version 2: August 2003