log1pf(3m) - osol9

1log1p(3M)               Mathematical Library Functions               log1p(3M)
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NAME

6       log1p, log1pf, log1pl - compute natural logarithm
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SYNOPSIS

9       c99 [ flag... ] file... -lm [ library... ]
10       #include <math.h>
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12       double log1p(double x);
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15       float log1pf(float x);
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18       long double log1pl(long double x);
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DESCRIPTION

22       These functions compute log(e)(1.0 + x).
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RETURN VALUES

25       Upon  successful  completion,  these functions return the natural loga‐
26       rithm of 1.0 + x.
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29       If x is −1, a pole error occurs and  log1p(),  log1pf(),  and  log1pl()
30       return −HUGE_VAL, −HUGE_VALF, and −HUGE_VALL, respectively.
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33       For finite values of x that are less than −1, or if x is −Inf, a domain
34       error occurs and a NaN is returned.
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37       If x is NaN, a NaN is returned.
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40       If x is ±0 or +Inf, x is returned.
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43       For exceptional cases, matherr(3M) tabulates the values to be  returned
44       by log1p() as specified by SVID3 and XPG3.
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ERRORS

47       These functions will fail if:
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49       Domain Error    The finite value of x is less than −1, or x is -Inf.
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51                       If   the   integer   expression   (math_errhandling   &
52                       MATH_ERREXCEPT) is non-zero, the invalid floating-point
53                       exception is raised.
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55                       The log1p() function sets errno to EDOM if the value of
56                       x is less than −1.
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59       Pole Error      The value of x is −1.
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61                       If   the   integer   expression   (math_errhandling   &
62                       MATH_ERREXCEPT)  is non-zero, the divide-by-zero float‐
63                       ing-point exception is raised.
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USAGE

67       An application wanting to check for exceptions should  call  feclearex‐
68       cept(FE_ALL_EXCEPT)  before  calling  these  functions.  On  return, if
69       fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is
70       non-zero,  an  exception  has been raised. An application should either
71       examine the return value or check the floating point exception flags to
72       detect exceptions.
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75       An  application  can  also  set  errno  to 0 before calling log1p(). On
76       return, if errno is non-zero, an error has occurred. The  log1pf()  and
77       log1pl() functions do not set errno.
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ATTRIBUTES

80       See attributes(5) for descriptions of the following attributes:
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85       ┌─────────────────────────────┬─────────────────────────────┐
86       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
87       ├─────────────────────────────┼─────────────────────────────┤
88       │Interface Stability          │Standard                     │
89       ├─────────────────────────────┼─────────────────────────────┤
90       │MT-Level                     │MT-Safe                      │
91       └─────────────────────────────┴─────────────────────────────┘
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