### 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**(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or
*cc -std=c99*

### DESCRIPTION

The
**fma**() function computes
*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.

### CONFORMING TO

C99, POSIX.1-2001.

### SEE ALSO

### COLOPHON

This page is part of release 3.23 of the Linux
*man-pages* project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.