bionic (3) lgamma.3posix.gz

Provided by: manpages-posix-dev_2013a-2_all bug

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


NAME
       lgamma, lgammaf, lgammal, signgam — log gamma function


SYNOPSIS
       #include <math.h>

       double lgamma(double x);
       float lgammaf(float x);
       long double lgammal(long double x);
       extern int signgam;


DESCRIPTION
       The  functionality  described  on  this  reference  page is aligned with the ISO C standard. Any conflict
       between the requirements described  here  and  the  ISO C  standard  is  unintentional.  This  volume  of
       POSIX.1‐2008 defers to the ISO C standard.

--

RETURN VALUE
       Upon successful completion, these functions shall return the logarithmic gamma of x.

       If x is a non-positive integer, a pole error shall occur and lgamma(),  lgammaf(),  and  lgammal()  shall
       return +HUGE_VAL, +HUGE_VALF, and +HUGE_VALL, respectively.

       If  the  correct  value  would  cause  overflow,  a  range error shall occur and lgamma(), lgammaf(), and
       lgammal() shall return ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (having the same sign as the correct value),
       respectively.

       If x is NaN, a NaN shall be returned.

       If x is 1 or 2, +0 shall be returned.

       If x is ±Inf, +Inf shall be returned.


ERRORS
       These functions shall fail if:

       Pole Error  The x argument is a negative integer or zero.

                   If  the  integer  expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be
                   set to [ERANGE].  If the integer expression (math_errhandling & MATH_ERREXCEPT) is  non-zero,
                   then the divide-by-zero floating-point exception shall be raised.

       Range Error The result overflows.

                   If  the  integer  expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be
                   set to [ERANGE].  If the integer expression (math_errhandling & MATH_ERREXCEPT) is  non-zero,
                   then the overflow floating-point exception shall be raised.

       The following sections are informative.


EXAMPLES
       None.


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


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       exp(), feclearexcept(), fetestexcept(), isnan()

       The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of Error Conditions for Mathematical
       Functions, <math.h>


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications  Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
       and The Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In  the  event
       of  any  discrepancy between this version and the original IEEE and The Open Group Standard, the original
       IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at
       http://www.unix.org/online.html .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .