log

 

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 Mathematical Library Functions                            log(3M)
 
 
 


NAME
      log - natural logarithm function
 


SYNOPSIS
      cc [ flag ... ] file ... -lm [ library ... ]
      #include <math.h>
 
      double log(double x);
 


DESCRIPTION
      The log() function computes  the  natural  logarithm  of  x,
      loge(x). The value of x must be positive.
 
 RETURN VALUES
      Upon successful completion, log() returns the natural  loga-
      rithm of x.
 
      If x is NaN, NaN is returned.
 
      If x is less than 0, -HUGE_VAL or NaN is returned and  errno
      is set to EDOM.
 
      If x is 0, -HUGE_VAL is returned and errno  may  be  set  to
      ERANGE.
 
      In IEEE754 mode (the -Xlibmieee cc compilation option), if x
      is  Inf  or  a quiet NaN, x is returned; if x is a signaling
      NaN, a quiet NaN  is  returned  and  the  invalid  operation
      exception is raised; if x is 1, 0 is returned; for all other
      positive x, a normalized number is returned and the  inexact
      exception is raised.
 
      For exceptional cases, matherr(3M) tabulates the  values  to
      be returned as dictated by Standards other than XPG4.
 
 ERRORS
      The log() function will fail if:
 
      EDOM  The value of x is negative.
 
      The log() function may fail if:
 
      ERANGE
            The value of x is 0.
 
      No other errors will occur.
 
 USAGE
      An application wishing to check for error situations  should
      set errno to 0 before calling log(). If errno is non-zero on
      return, or the return value is NaN, an error has occurred.
 
 
 
 
 SunOS 5.8           Last change: 29 Dec 1996                    1
 
 
 
 
 
 
 Mathematical Library Functions                            log(3M)
 
 
 


ATTRIBUTES
      See attributes(5) for descriptions of the  following  attri-
      butes:
 
      ____________________________________________________________
     |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
     |_____________________________|_____________________________|
     | MT-Level                    | MT-Safe                     |
     |_____________________________|_____________________________|
 
 


SEE ALSO
      exp(3M),  isnan(3M),  log10(3M),   log1p(3M),   matherr(3M),
      attributes(5), standards(5)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 SunOS 5.8           Last change: 29 Dec 1996                    2
 
 
 

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