# FMA

## NAME

fma, fmaf, fmal - floating-point multiply and add

## 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)**.

## CONFORMING TO

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

## SEE ALSO

**remainder(3)**, **remquo(3)**

## COLOPHON

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