1EXP(3P)                    POSIX Programmer's Manual                   EXP(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       exp, expf, expl - exponential function
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SYNOPSIS

15       #include <math.h>
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17       double exp(double x);
18       float expf(float x);
19       long double expl(long double x);
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21

DESCRIPTION

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

32       Upon successful completion, these functions shall return  the  exponen‐
33       tial value of x.
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35       If  the  correct  value would cause overflow, a range error shall occur
36       and exp(), expf(), and expl() shall  return  the  value  of  the  macro
37       HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
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39       If the correct value would cause underflow, and is not representable, a
40       range error may occur, and  either 0.0 (if supported), or an  implemen‐
41       tation-defined value shall be returned.
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43       If x is NaN, a NaN shall be returned.
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45       If x is ±0, 1 shall be returned.
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47       If x is -Inf, +0 shall be returned.
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49       If x is +Inf, x shall be returned.
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51       If  the  correct  value  would cause underflow, and is representable, a
52       range error may occur and the correct value shall be returned.
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ERRORS

55       These functions shall fail if:
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57       Range Error
58              The result overflows.
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60       If the integer expression (math_errhandling & MATH_ERRNO) is  non-zero,
61       then  errno  shall  be  set  to  [ERANGE].  If  the  integer expression
62       (math_errhandling & MATH_ERREXCEPT)  is  non-zero,  then  the  overflow
63       floating-point exception shall be raised.
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66       These functions may fail if:
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68       Range Error
69              The result underflows.
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71       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
72       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression
73       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero, then the underflow
74       floating-point exception shall be raised.
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77       The following sections are informative.
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EXAMPLES

80       None.
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APPLICATION USAGE

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

91       None.
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FUTURE DIRECTIONS

94       None.
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SEE ALSO

97       feclearexcept(),  fetestexcept(),  isnan(), log(), the Base Definitions
98       volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Condi‐
99       tions for Mathematical Functions, <math.h>
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102       Portions  of  this text are reprinted and reproduced in electronic form
103       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
104       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
105       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
106       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
107       event of any discrepancy between this version and the original IEEE and
108       The  Open Group Standard, the original IEEE and The Open Group Standard
109       is the referee document. The original Standard can be  obtained  online
110       at http://www.opengroup.org/unix/online.html .
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114IEEE/The Open Group                  2003                              EXP(3P)
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