mirror of https://github.com/mkerrisk/man-pages
146 lines
2.9 KiB
Groff
146 lines
2.9 KiB
Groff
.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
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.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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.\" <mtk.manpages@gmail.com>
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.\" Distributed under GPL, 2002-07-27 Walter Harms
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.\" Modified 2004-11-15, Added further text on FLT_ROUNDS
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.\" as suggested by AEB and Fabian Kreutz
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.\"
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.TH FMA 3 2008-08-11 "" "Linux Programmer's Manual"
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.SH NAME
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fma, fmaf, fmal \- floating-point multiply and add
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.SH SYNOPSIS
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.nf
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.B #include <math.h>
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.sp
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.BI "double fma(double " x ", double " y ", double " z );
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.br
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.BI "float fmaf(float " x ", float " y ", float " z );
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.br
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.BI "long double fmal(long double " x ", long double " y ", long double " z );
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.fi
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.sp
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Link with \fI\-lm\fP.
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.ad l
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.BR fma (),
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.BR fmaf (),
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.BR fmal ():
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_XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.ad b
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.SH DESCRIPTION
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The
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.BR fma ()
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function computes
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.IR x " * " y " + " z .
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The result is rounded as one ternary operation according to the
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current rounding mode (see
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.BR fenv (3)).
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.SH RETURN VALUE
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These functions return the value of
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.IR x " * " y " + " z ,
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rounded as one ternary operation.
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If
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.I x
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or
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.I y
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is a NaN, a NaN is returned.
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If
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.I x
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times
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.I y
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is an exact infinity, and
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.I z
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is an infinity with the opposite sign,
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a domain error occurs,
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and a NaN is returned.
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If one of
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.I x
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or
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.I y
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is an infinity, the other is 0, and
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.I z
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is not a NaN,
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a domain error occurs, and
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a NaN is returned.
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If one of
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.I x
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or
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.I y
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is an infinity, and the other is 0, and
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.I z
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is a NaN,
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.\" POSIX.1 makes the domain error optional for this case.
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a domain error occurs, and
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a NaN is returned.
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If
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.I x
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times
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.I y
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is not an infinity times zero (or vice versa), and
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.I z
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is a NaN,
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a NaN is returned.
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If the result overflows,
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a range error occurs, and
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an infinity with the correct sign is returned.
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If the result underflows,
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a range error occurs, and
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a signed 0 is returned.
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.SH ERRORS
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See
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.BR math_error (7)
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for information on how to determine whether an error has occurred
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when calling these functions.
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.PP
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The following errors can occur:
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.TP
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Domain error: \fIx\fP * \fIy\fP + \fIz\fP, \
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or \fIx\fP * \fIy\fP is invalid and \fIz\fP is not a NaN
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.\" .I errno
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.\" is set to
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.\" .BR EDOM .
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An invalid floating-point exception
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.RB ( FE_INVALID )
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is raised.
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.TP
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Range error: result overflow
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.\" .I errno
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.\" is set to
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.\" .BR ERANGE .
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An overflow floating-point exception
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.RB ( FE_OVERFLOW )
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is raised.
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.TP
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Range error: result underflow
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.\" .I errno
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.\" is set to
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.\" .BR ERANGE .
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An underflow floating-point exception
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.RB ( FE_UNDERFLOW )
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is raised.
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.PP
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These functions do not set
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.IR errno .
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.\" FIXME . Is it intentional that these functions do not set errno?
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.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6801
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.SH VERSIONS
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These functions first appeared in glibc in version 2.1.
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.SH "CONFORMING TO"
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C99, POSIX.1-2001.
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.SH "SEE ALSO"
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.BR remainder (3),
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.BR remquo (3)
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