nextafter, nextafterf, nextafterl, _nextafter, _nextafterf, nexttoward, nexttowardf, nexttowardl

Article
06/05/2017

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The latest version of this topic can be found at nextafter, nextafterf, nextafterl, _nextafter, _nextafterf, nexttoward, nexttowardf, nexttowardl.

Returns the next representable floating-point value.

Syntax

double nextafter(  
   double x,  
   double y   
);  
  
float nextafter(  
   float x,  
   float y   
); /* C++ only, requires <cmath> */  
  
long double nextafter(  
   long double x,  
   long double y   
); /* C++ only, requires <cmath> */  
  
float nextafterf(  
   float x,  
   float y   
);   
  
long double nextafterl(  
   long double x,  
   long double y   
);  
  
double _nextafter(  
   double x,  
   double y   
);  
  
float _nextafterf(  
   float x,  
   float y   
); /* x64 only */  
  
double nexttoward(  
   double x,  
   long double y   
);  
  
float nexttoward(  
   float x,  
   long double y   
); /* C++ only, requires <cmath> */  
  
long double nexttoward(  
   long double x,  
   long double y   
); /* C++ only, requires <cmath> */  
  
float nexttowardf(  
   float x,  
   long double y   
);   
  
long double nexttowardl(  
   long double x,  
   long double y   
);

Parameters

x
The floating-point value to start from.

y
The floating-point value to go towards.

Return Value

Returns the next representable floating-point value of the return type after x in the direction of y. If x=y, the function returns y, converted to the return type, with no exception triggered. If x is not equal to y, and the result is a denormal or zero, the FE_UNDERFLOW and FE_INEXACT floating-point exception states are set, and the correct result is returned. If either x or y is a NAN, then the return value is one of the input NANs. If x is finite and the result is infinite or not representable in the type, a correctly signed infinity or NAN is returned, the FE_OVERFLOW and FE_INEXACT floating-point exception states are set, and errno is set to ERANGE.

Remarks

The nextafter and nexttoward function families are equivalent, except for the parameter type of y. If x and y are equal, the value returned is y converted to the return type.

Because C++ allows overloading, if you include <cmath> you can call overloads of nextafter and nexttoward that return float and long double types. In a C program, nextafter and nexttoward always return double.

The _nextafter and _nextafterf functions are Microsoft specific. The _nextafterf function is only available when compiling for x64.

Requirements

Routine	Required header (C)	Required header (C++)
`nextafter`, `nextafterf`, `nextafterl`, `_nextafterf`, `nexttoward`, `nexttowardf`, `nexttowardl`	<math.h>	<math.h> or <cmath>
`_nextafter`	<float.h>	<float.h> or <cfloat>

For more compatibility information, see Compatibility in the Introduction.

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