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diff --git a/man3/lgamma.3 b/man3/lgamma.3 new file mode 100644 index 0000000..cbcf363 --- /dev/null +++ b/man3/lgamma.3 @@ -0,0 +1,202 @@ +.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de) +.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk +.\" <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: GPL-1.0-or-later +.\" +.\" based on glibc infopages +.\" +.TH lgamma 3 2023-03-30 "Linux man-pages 6.05.01" +.SH NAME +lgamma, lgammaf, lgammal, lgamma_r, lgammaf_r, lgammal_r, signgam \- +log gamma function +.SH LIBRARY +Math library +.RI ( libm ", " \-lm ) +.SH SYNOPSIS +.nf +.B #include <math.h> +.PP +.BI "double lgamma(double " x ); +.BI "float lgammaf(float " x ); +.BI "long double lgammal(long double " x ); +.PP +.BI "double lgamma_r(double " x ", int *" signp ); +.BI "float lgammaf_r(float " x ", int *" signp ); +.BI "long double lgammal_r(long double " x ", int *" signp ); +.PP +.BI "extern int " signgam ; +.fi +.PP +.RS -4 +Feature Test Macro Requirements for glibc (see +.BR feature_test_macros (7)): +.RE +.PP +.nf +.BR lgamma (): + _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE + || /* Since glibc 2.19: */ _DEFAULT_SOURCE + || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE +.fi +.PP +.BR lgammaf (), +.BR lgammal (): +.nf + _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L + || /* Since glibc 2.19: */ _DEFAULT_SOURCE + || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE +.fi +.PP +.BR lgamma_r (), +.BR lgammaf_r (), +.BR lgammal_r (): +.nf + /* Since glibc 2.19: */ _DEFAULT_SOURCE + || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE +.fi +.PP +.IR signgam : +.nf + _XOPEN_SOURCE + || /* Since glibc 2.19: */ _DEFAULT_SOURCE + || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE +.fi +.SH DESCRIPTION +For the definition of the Gamma function, see +.BR tgamma (3). +.PP +The +.BR lgamma (), +.BR lgammaf (), +and +.BR lgammal () +functions return the natural logarithm of +the absolute value of the Gamma function. +The sign of the Gamma function is returned in the +external integer +.I signgam +declared in +.IR <math.h> . +It is 1 when the Gamma function is positive or zero, \-1 +when it is negative. +.PP +Since using a constant location +.I signgam +is not thread-safe, the functions +.BR lgamma_r (), +.BR lgammaf_r (), +and +.BR lgammal_r () +have been introduced; they return the sign via the argument +.IR signp . +.SH RETURN VALUE +On success, these functions return the natural logarithm of Gamma(x). +.PP +If +.I x +is a NaN, a NaN is returned. +.PP +If +.I x +is 1 or 2, +0 is returned. +.PP +If +.I x +is positive infinity or negative infinity, +positive infinity is returned. +.PP +If +.I x +is a nonpositive integer, +a pole error occurs, +and the functions return +.RB + HUGE_VAL , +.RB + HUGE_VALF , +or +.RB + HUGE_VALL , +respectively. +.PP +If the result overflows, +a range error occurs, +.\" e.g., lgamma(DBL_MAX) +and the functions return +.BR HUGE_VAL , +.BR HUGE_VALF , +or +.BR HUGE_VALL , +respectively, with the correct mathematical sign. +.SH ERRORS +See +.BR math_error (7) +for information on how to determine whether an error has occurred +when calling these functions. +.PP +The following errors can occur: +.TP +Pole error: \fIx\fP is a nonpositive integer +.I errno +is set to +.B ERANGE +(but see BUGS). +A divide-by-zero floating-point exception +.RB ( FE_DIVBYZERO ) +is raised. +.TP +Range error: result overflow +.I errno +is set to +.BR ERANGE . +An overflow floating-point exception +.RB ( FE_OVERFLOW ) +is raised. +.\" glibc (as at 2.8) also supports an inexact +.\" exception for various cases. +.SH STANDARDS +.TP +.BR lgamma () +.TQ +.BR lgammaf () +.TQ +.BR lgammal () +C11, POSIX.1-2008. +.TP +.I signgam +POSIX.1-2008. +.TP +.BR lgamma_r () +.TQ +.BR lgammaf_r () +.TQ +.BR lgammal_r () +None. +.SH HISTORY +.TP +.BR lgamma () +.TQ +.BR lgammaf () +.TQ +.BR lgammal () +C99, POSIX.1-2001. +.TP +.I signgam +POSIX.1-2001. +.TP +.BR lgamma_r () +.TQ +.BR lgammaf_r () +.TQ +.BR lgammal_r () +None. +.SH BUGS +In glibc 2.9 and earlier, +.\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6777 +when a pole error occurs, +.I errno +is set to +.BR EDOM ; +instead of the POSIX-mandated +.BR ERANGE . +Since glibc 2.10, glibc does the right thing. +.SH SEE ALSO +.BR tgamma (3) |