exp(P)                                                   exp(P)





NAME
       exp, expf, expl - exponential function

SYNOPSIS
       #include <math.h>

       double exp(double x);
       float expf(float x);
       long double expl(long double x);


DESCRIPTION
       The  functionality  described  on this reference page is
       aligned with the ISO C standard.  Any  conflict  between
       the  requirements  described here and the ISO C standard
       is unintentional.  This volume  of  IEEE Std 1003.1-2001
       defers to the ISO C standard.

       These functions shall compute the base- e exponential of
       x.

       An application wishing to  check  for  error  situations
       should   set   errno   to   zero   and  call  feclearex-
       cept(FE_ALL_EXCEPT) before calling these functions.   On
       return,  if errno is non-zero or fetestexcept(FE_INVALID
       | FE_DIVBYZERO | FE_OVERFLOW  |  FE_UNDERFLOW)  is  non-
       zero, an error has occurred.

RETURN VALUE
       Upon successful completion, these functions shall return
       the exponential value of x.

       If the correct value would cause overflow, a range error
       shall  occur  and exp(), expf(), and expl() shall return
       the  value  of  the  macro  HUGE_VAL,   HUGE_VALF,   and
       HUGE_VALL, respectively.

       If  the  correct value would cause underflow, and is not
       representable, a range error may  occur,  and     either
       0.0 (if supported), or   an implementation-defined value
       shall be returned.

       If x is NaN, a NaN shall be returned.

       If x is +-0, 1 shall be returned.

       If x is -Inf, +0 shall be returned.

       If x is +Inf, x shall be returned.

       If the correct value would cause underflow, and is  rep-
       resentable,  a  range  error  may  occur and the correct
       value shall be returned.

ERRORS
       These functions shall fail if:

       Range Error
              The result overflows.

       If   the   integer   expression   (math_errhandling    &
       MATH_ERRNO)  is  non-zero,  then  errno  shall be set to
       [ERANGE]. If the integer expression (math_errhandling  &
       MATH_ERREXCEPT) is non-zero, then the overflow floating-
       point exception shall be raised.


       These functions may fail if:

       Range Error
              The result underflows.

       If   the   integer   expression   (math_errhandling    &
       MATH_ERRNO)  is  non-zero,  then  errno  shall be set to
       [ERANGE]. If the integer expression (math_errhandling  &
       MATH_ERREXCEPT)  is  non-zero, then the underflow float-
       ing-point exception shall be raised.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       Note  that  for  IEEE Std 754-1985  double,  709.8  <  x
       implies  exp(  x)  has  overflowed. The value x < -708.4
       implies exp( x) has underflowed.

       On   error,   the   expressions   (math_errhandling    &
       MATH_ERRNO)  and (math_errhandling & MATH_ERREXCEPT) are
       independent of each other, but at least one of them must
       be non-zero.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       feclearexcept() , fetestexcept() , isnan() , log() , the
       Base Definitions volume of IEEE Std 1003.1-2001, Section
       4.18,  Treatment  of  Error  Conditions for Mathematical
       Functions, <math.h>

COPYRIGHT
       Portions of this text are reprinted  and  reproduced  in
       electronic  form  from  IEEE  Std  1003.1, 2003 Edition,
       Standard for Information Technology -- Portable  Operat-
       ing System Interface (POSIX), The Open Group Base Speci-
       fications Issue 6, Copyright (C) 2001-2003 by the Insti-
       tute  of  Electrical  and Electronics Engineers, Inc and
       The Open Group. In the event of any discrepancy  between
       this  version  and  the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group  Standard
       is  the  referee  document. The original Standard can be
       obtained        online        at        http://www.open-
       group.org/unix/online.html .



POSIX                         2003                       exp(P)
