1expm1(3M)               Mathematical Library Functions               expm1(3M)
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NAME

6       expm1, expm1f, expm1l - compute exponential function
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SYNOPSIS

9       c99 [ flag... ] file... -lm [ library... ]
10       #include <math.h>
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12       double expm1(double x);
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15       float expm1f(float x);
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18       long double expm1l(long double x);
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DESCRIPTION

22       These functions compute e^x−1.0.
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RETURN VALUES

25       Upon successful completion, these functions return e^x−1.0.
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28       If x is NaN, a NaN is returned.
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31       If x is ±0, ±0 is returned.
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34       If x is −Inf, −1 is returned.
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37       If x is +Inf, x is returned.
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ERRORS

40       These functions will fail if:
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42       Range Error    The result overflows.
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44                      If    the   integer   expression   (math_errhandling   &
45                      MATH_ERREXCEPT) is non-zero, the overflow floating-point
46                      exception is raised.
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USAGE

50       The  value  of  expm1(x) can be more accurate than exp(x)−1.0 for small
51       values of x.
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54       The expm1() and log1p(3M) functions are useful for  financial  calcula‐
55       tions of ((1+x)^n−1)/x, namely:
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57         expm1(n * log1p(x))/x
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61       when  x is very small (for example, when performing calculations with a
62       small daily interest rate).   These  functions  also  simplify  writing
63       accurate inverse hyperbolic functions.
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66       An  application  wanting to check for exceptions should call feclearex‐
67       cept(FE_ALL_EXCEPT) before  calling  these  functions.  On  return,  if
68       fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is
69       non-zero, an exception has been raised. An  application  should  either
70       examine the return value or check the floating point exception flags to
71       detect exceptions.
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ATTRIBUTES

74       See attributes(5) for descriptions of the following attributes:
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79       ┌─────────────────────────────┬─────────────────────────────┐
80       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
81       ├─────────────────────────────┼─────────────────────────────┤
82       │Interface Stability          │Standard                     │
83       ├─────────────────────────────┼─────────────────────────────┤
84       │MT-Level                     │MT-Safe                      │
85       └─────────────────────────────┴─────────────────────────────┘
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SEE ALSO

88       exp(3M),  feclearexcept(3M),  fetestexcept(3M),  ilogb(3M),  log1p(3M),
89       math.h(3HEAD), attributes(5), standards(5)
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93SunOS 5.11                        12 Jul 2006                        expm1(3M)
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