# NAME

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

# LIBRARY

Math library (`libm`, `-lm`)

# 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);``````

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`.

# ATTRIBUTES

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

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

# STANDARDS

C11, POSIX.1-2008.

# HISTORY

glibc 2.1. C99, POSIX.1-2001.