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EXP(3P)                    POSIX Programmer's Manual                   EXP(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
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
       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  feclearexcept(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  exponen-
       tial 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  implemen-
       tation-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 representable, 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
       floating-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 Condi-
       tions 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  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  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.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                              EXP(3P)