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fma, fmaf, fmal

 

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Multiplies two values together, adds a third value, and then rounds the result, without losing any precision due to intermediary rounding.

Syntax

double fma(  
   double x,   
   double y,   
   double z  
);  
  
float fma(  
   float  x,   
   float  y,   
   float z  
); //C++ only  
  
long double fma(  
   long double  x,   
   long double  y,   
   long double z  
); //C++ only  
  
float fmaf(  
   float  x,   
   float  y,   
   float z  
);  
  
long double fmal(  
   long double  x,   
   long double  y,   
   long double z  
);  
  

Parameters

[in] x
The first value to multiply.

[in] y
The second value to multiply.

[in] z
The value to add.

Return Value

Returns (x × y) + z. The return value is then rounded using the current rounding format.

Otherwise, may return one of the following values:

Issue Return
x = INFINITY, y = 0 or

 x = 0, y = INFINITY
NaN
x or y = exact ± INFINITY, z = INFINITY with the opposite sign NaN
x or y = NaN NaN
not (x = 0, y= indefinite) and z = NaN

not (x=indefinite, y=0) and z = NaN
NaN
Overflow range error ±HUGE_VAL, ±HUGE_VALF, or ±HUGE_VALL
Underflow range error correct value, after rounding.

Errors are reported as specified in _matherr.

Remarks

Because C++ allows overloading, you can call overloads of fma that take and return float and long double types. In a C program, fma always takes and returns a double.

This function computes the value as though it were taken to infinite precision, and then rounds the final result.

Requirements

Function C header C++ header
fma, fmaf, fmal <math.h> <cmath>

For additional compatibility information, see Compatibility.

See Also

Alphabetical Function Reference
remainder, remainderf, remainderl
remquo, remquof, remquol