mirror of https://github.com/mkerrisk/man-pages
125 lines
4.2 KiB
Plaintext
125 lines
4.2 KiB
Plaintext
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "TGAMMA" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" tgamma
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.SH NAME
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tgamma, tgammaf, tgammal \- compute gamma() function
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.SH SYNOPSIS
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.LP
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\fB#include <math.h>
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.br
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.sp
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double tgamma(double\fP \fIx\fP\fB);
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.br
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float tgammaf(float\fP \fIx\fP\fB);
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.br
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long double tgammal(long double\fP \fIx\fP\fB);
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.br
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\fP
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.SH DESCRIPTION
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.LP
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These functions shall compute the \fIgamma\fP() function of \fIx\fP.
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.LP
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An application wishing to check for error situations should set \fIerrno\fP
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to zero and call
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\fIfeclearexcept\fP(FE_ALL_EXCEPT) before calling these functions.
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On return, if \fIerrno\fP is non-zero or
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\fIfetestexcept\fP(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
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is non-zero, an error has occurred.
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.SH RETURN VALUE
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.LP
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Upon successful completion, these functions shall return \fIGamma\fP(
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\fIx\fP).
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.LP
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If \fIx\fP is a negative integer, a domain error shall occur, and
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either a NaN (if supported), or an implementation-defined
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value shall be returned.
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.LP
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If the correct value would cause overflow, a range error shall occur
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and \fItgamma\fP(), \fItgammaf\fP(), and \fItgammal\fP()
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shall return \(+-HUGE_VAL, \(+-HUGE_VALF, or \(+-HUGE_VALL, respectively,
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with the same sign as the correct value of
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the function.
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.LP
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If
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\fIx\fP is NaN, a NaN shall be returned.
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.LP
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If \fIx\fP is +Inf, \fIx\fP shall be returned.
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.LP
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If \fIx\fP is \(+-0, a pole error shall occur, and \fItgamma\fP(),
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\fItgammaf\fP(), and \fItgammal\fP() shall return
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\(+-HUGE_VAL, \(+-HUGE_VALF, and \(+-HUGE_VALL, respectively.
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.LP
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If \fIx\fP is -Inf, a domain error shall occur, and either a NaN (if
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supported), or an implementation-defined value shall be
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returned.
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.SH ERRORS
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.LP
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These functions shall fail if:
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.TP 7
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Domain\ Error
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The value of \fIx\fP is a negative integer, \ or \fIx\fP is -Inf.
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.LP
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If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
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then \fIerrno\fP shall be set to [EDOM]. If the
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integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
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then the invalid floating-point exception shall be
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raised.
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.TP 7
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Pole\ Error
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The value of \fIx\fP is zero.
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.LP
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If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
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then \fIerrno\fP shall be set to [ERANGE]. If the
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integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
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then the divide-by-zero floating-point exception shall be
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raised.
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.br
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.TP 7
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Range\ Error
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The value overflows.
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.LP
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If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
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then \fIerrno\fP shall be set to [ERANGE]. If the
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integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
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then the overflow floating-point exception shall be
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raised.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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For IEEE\ Std\ 754-1985 \fBdouble\fP, overflow happens when 0 < \fIx\fP
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< 1/DBL_MAX, and 171.7 <
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\fIx\fP.
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.LP
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On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling
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& MATH_ERREXCEPT) are independent of
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each other, but at least one of them must be non-zero.
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.SH RATIONALE
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.LP
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This function is named \fItgamma\fP() in order to avoid conflicts
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with the historical \fIgamma\fP() and \fIlgamma\fP() functions.
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.SH FUTURE DIRECTIONS
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.LP
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It is possible that the error response for a negative integer argument
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may be changed to a pole error and a return value of
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\(+-Inf.
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.SH SEE ALSO
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.LP
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\fIfeclearexcept\fP() , \fIfetestexcept\fP() , \fIlgamma\fP() , the
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Base Definitions volume of IEEE\ Std\ 1003.1-2001, Section 4.18, Treatment
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of Error Conditions for Mathematical Functions, \fI<math.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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