# fmaf (3)

# NAME

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

#include <math.h>

Link withdouble fma(doublex, doubley, doublez);float fmaf(floatx, floaty, floatz);long double fmal(long doublex, long doubley, long doublez);

*-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.

*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.# SEE ALSO

**remainder**(3),

**remquo**(3)