man fmal (3): floating-point multiply and add

Other Alias

fma, fmaf

SYNOPSIS

#include <math.h>

double fma(double x, double y, double z);
float fmaf(float x, float y, float z);
long double fmal(long double x, long double y, long double z);

Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

fma(), fmaf(), fmal():

: _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION

These functions compute x * y + z. The result is rounded as one ternary operation according to the current rounding mode (see fenv(3)).

RETURN VALUE

These functions return the value of x * y + z, rounded as one ternary operation.

If x or y is a NaN, a NaN is returned.

If x times y is an exact infinity, and z is an infinity with the opposite sign, a domain error occurs, and a NaN is returned.

If one of x or y is an infinity, the other is 0, and z is not a NaN, a domain error occurs, and a NaN is returned.

If one of x or y is an infinity, and the other is 0, and z is a NaN, a domain error occurs, and a NaN is returned.

If x times y is not an infinity times zero (or vice versa), and z is a NaN, a NaN is returned.

If the result overflows, a range error occurs, and an infinity with the correct sign is returned.

If the result underflows, a range error occurs, and a signed 0 is returned.

ERRORS

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

Domain error: x * y + z, or x * y is invalid and z is not a NaN: An invalid floating-point exception (FE_INVALID) is raised.
Range error: result overflow: An overflow floating-point exception (FE_OVERFLOW) is raised.
Range error: result underflow: An underflow floating-point exception (FE_UNDERFLOW) is raised.

These functions do not set errno.

VERSIONS

These functions first appeared in glibc in version 2.1.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
fma(), fmaf(), fmal()	Thread safety	MT-Safe

CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.

COLOPHON

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