1LOG10(P)                   POSIX Programmer's Manual                  LOG10(P)
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NAME

6       log10, log10f, log10l - base 10 logarithm function
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SYNOPSIS

9       #include <math.h>
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11       double log10(double x);
12       float log10f(float x);
13       long double log10l(long double x);
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15

DESCRIPTION

17       These  functions  shall compute the base 10 logarithm of their argument
18       x, log_10(x).
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20       An application wishing to check for error situations should  set  errno
21       to  zero  and  call  feclearexcept(FE_ALL_EXCEPT)  before calling these
22       functions.  On return, if errno is non-zero or  fetestexcept(FE_INVALID
23       |  FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
24       occurred.
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RETURN VALUE

27       Upon successful completion, these functions shall return  the  base  10
28       logarithm of x.
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30       If  x  is  ±0,  a  pole  error  shall  occur and log10(), log10f(), and
31       log10l() shall return -HUGE_VAL, -HUGE_VALF,  and  -HUGE_VALL,  respec‐
32       tively.
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34       For  finite  values  of  x that are less than 0,    or if x is -Inf,  a
35       domain error shall occur, and    either a NaN (if supported),  or    an
36       implementation-defined value shall be returned.
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38       If x is NaN, a NaN shall be returned.
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40       If x is 1, +0 shall be returned.
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42       If x is +Inf, +Inf shall be returned.
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ERRORS

45       These functions shall fail if:
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47       Domain Error
48              The finite value of x is negative,    or x is -Inf.
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50       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
51       then  errno  shall  be  set  to  [EDOM].  If  the  integer   expression
52       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then  the invalid
53       floating-point exception shall be raised.
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55       Pole Error
56              The value of x is zero.
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58       If the integer expression (math_errhandling & MATH_ERRNO) is  non-zero,
59       then  errno  shall  be  set  to  [ERANGE].  If  the  integer expression
60       (math_errhandling & MATH_ERREXCEPT) is non-zero,  then  the  divide-by-
61       zero floating-point exception shall be raised.
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64       The following sections are informative.
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EXAMPLES

67       None.
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APPLICATION USAGE

70       On   error,   the   expressions  (math_errhandling  &  MATH_ERRNO)  and
71       (math_errhandling & MATH_ERREXCEPT) are independent of each other,  but
72       at least one of them must be non-zero.
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RATIONALE

75       None.
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FUTURE DIRECTIONS

78       None.
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SEE ALSO

81       feclearexcept()  ,  fetestexcept() , isnan() , log() , pow() , the Base
82       Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment  of
83       Error Conditions for Mathematical Functions, <math.h>
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86       Portions  of  this text are reprinted and reproduced in electronic form
87       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
88       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
89       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
90       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
91       event of any discrepancy between this version and the original IEEE and
92       The  Open Group Standard, the original IEEE and The Open Group Standard
93       is the referee document. The original Standard can be  obtained  online
94       at http://www.opengroup.org/unix/online.html .
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98IEEE/The Open Group                  2003                             LOG10(P)
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