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+.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
+.TH "LGAMMA" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
+.\" lgamma 
+.SH NAME
+lgamma, lgammaf, lgammal \- log gamma function
+.SH SYNOPSIS
+.LP
+\fB#include <math.h>
+.br
+.sp
+double lgamma(double\fP \fIx\fP\fB);
+.br
+float lgammaf(float\fP \fIx\fP\fB);
+.br
+long double lgammal(long double\fP \fIx\fP\fB);
+.br
+\fP
+.LP
+\fBextern int signgam; \fP
+\fB
+.br
+\fP
+.SH DESCRIPTION
+.LP
+These functions shall compute 
+.sp
+.sp
+The argument \fIx\fP need not be a non-positive integer (Gamma(x)
+is defined over the reals,
+except the non-positive integers).
+.LP
+The sign of Gamma(x) is returned in the external integer \fIsigngam\fP.
+.LP
+These functions need not be reentrant. A function that is not required
+to be reentrant is not required to be thread-safe. 
+.LP
+An application wishing to check for error situations should set \fIerrno\fP
+to zero and call
+\fIfeclearexcept\fP(FE_ALL_EXCEPT) before calling these functions.
+On return, if \fIerrno\fP is non-zero or
+\fIfetestexcept\fP(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
+is non-zero, an error has occurred.
+.SH RETURN VALUE
+.LP
+Upon successful completion, these functions shall return the logarithmic
+gamma of \fIx\fP.
+.LP
+If \fIx\fP is a non-positive integer, a pole error shall occur and
+\fIlgamma\fP(), \fIlgammaf\fP(), and \fIlgammal\fP()
+shall return +HUGE_VAL, +HUGE_VALF, and +HUGE_VALL, respectively.
+.LP
+If the correct value would cause overflow, a range error shall occur
+and \fIlgamma\fP(), \fIlgammaf\fP(), and \fIlgammal\fP()
+shall return \(+-HUGE_VAL, \(+-HUGE_VALF, and \(+-HUGE_VALL (having
+the same sign as the correct value),
+respectively.
+.LP
+If
+\fIx\fP is NaN, a NaN shall be returned.
+.LP
+If \fIx\fP is 1 or 2, +0 shall be returned.
+.LP
+If \fIx\fP is \(+-Inf, +Inf shall be returned. 
+.SH ERRORS
+.LP
+These functions shall fail if:
+.TP 7
+Pole\ Error
+The \fIx\fP argument is a negative integer or zero. 
+.LP
+If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
+then \fIerrno\fP 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.
+.TP 7
+Range\ Error
+The result overflows. 
+.LP
+If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
+then \fIerrno\fP 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.
+.sp
+.LP
+\fIThe following sections are informative.\fP
+.SH EXAMPLES
+.LP
+None.
+.SH APPLICATION USAGE
+.LP
+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.
+.SH RATIONALE
+.LP
+None.
+.SH FUTURE DIRECTIONS
+.LP
+None.
+.SH SEE ALSO
+.LP
+\fIexp\fP() , \fIfeclearexcept\fP() , \fIfetestexcept\fP() , \fIisnan\fP()
+, the Base Definitions volume of
+IEEE\ Std\ 1003.1-2001, Section 4.18, Treatment of Error Conditions
+for
+Mathematical Functions, \fI<math.h>\fP
+.SH COPYRIGHT
+Portions of this text are reprinted and reproduced in electronic form
+from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
+-- Portable Operating System Interface (POSIX), The Open Group Base
+Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
+Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .