1EXP(P)                     POSIX Programmer's Manual                    EXP(P)
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NAME

6       exp, expf, expl - exponential function
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SYNOPSIS

9       #include <math.h>
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11       double exp(double x);
12       float expf(float x);
13       long double expl(long double x);
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15

DESCRIPTION

17       These functions shall compute the base- e exponential of x.
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19       An  application  wishing to check for error situations should set errno
20       to zero and  call  feclearexcept(FE_ALL_EXCEPT)  before  calling  these
21       functions.   On return, if errno is non-zero or fetestexcept(FE_INVALID
22       | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error  has
23       occurred.
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RETURN VALUE

26       Upon  successful  completion, these functions shall return the exponen‐
27       tial value of x.
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29       If the correct value would cause overflow, a range  error  shall  occur
30       and  exp(),  expf(),  and  expl()  shall  return the value of the macro
31       HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
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33       If the correct value would cause underflow, and is not representable, a
34       range error may occur, and    either 0.0 (if supported), or   an imple‐
35       mentation-defined value shall be returned.
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37       If x is NaN, a NaN shall be returned.
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39       If x is ±0, 1 shall be returned.
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41       If x is -Inf, +0 shall be returned.
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43       If x is +Inf, x shall be returned.
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45       If the correct value would cause underflow,  and  is  representable,  a
46       range error may occur and the correct value shall be returned.
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ERRORS

49       These functions shall fail if:
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51       Range Error
52              The result overflows.
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54       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
55       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression
56       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then the overflow
57       floating-point exception shall be raised.
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59
60       These functions may fail if:
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62       Range Error
63              The result underflows.
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65       If the integer expression (math_errhandling & MATH_ERRNO) is  non-zero,
66       then  errno  shall  be  set  to  [ERANGE].  If  the  integer expression
67       (math_errhandling & MATH_ERREXCEPT) is  non-zero,  then  the  underflow
68       floating-point exception shall be raised.
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70
71       The following sections are informative.
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EXAMPLES

74       None.
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APPLICATION USAGE

77       Note  that  for IEEE Std 754-1985 double, 709.8 < x implies exp( x) has
78       overflowed. The value x < -708.4 implies exp( x) has underflowed.
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80       On  error,  the  expressions  (math_errhandling   &   MATH_ERRNO)   and
81       (math_errhandling  & MATH_ERREXCEPT) are independent of each other, but
82       at least one of them must be non-zero.
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RATIONALE

85       None.
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FUTURE DIRECTIONS

88       None.
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SEE ALSO

91       feclearexcept() , fetestexcept() , isnan() , log() , the  Base  Defini‐
92       tions  volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error
93       Conditions for Mathematical Functions, <math.h>
94

96       Portions of this text are reprinted and reproduced in  electronic  form
97       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
98       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
99       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
100       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
101       event of any discrepancy between this version and the original IEEE and
102       The Open Group Standard, the original IEEE and The Open Group  Standard
103       is  the  referee document. The original Standard can be obtained online
104       at http://www.opengroup.org/unix/online.html .
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108IEEE/The Open Group                  2003                               EXP(P)
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