## table of contents

fma(3) | Library Functions Manual | fma(3) |

# NAME¶

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

# LIBRARY¶

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

# SYNOPSIS¶

#include <math.h>

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

**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.

# SEE ALSO¶

2024-05-02 | Linux man-pages 6.8 |