nextafter-functions.md

title	description	ms.date	api_name	api_location	api_type	topic_type	f1_keywords	helpviewer_keywords
nextafter, nextafterf, nextafterl, _nextafter, _nextafterf, nexttoward, nexttowardf, nexttowardl	API reference for nextafter, nextafterf, nextafterl, _nextafter, _nextafterf, nexttoward, nexttowardf, and nexttowardl; which return the next representable floating-point value.	1/15/2021	nextafterf _nextafterf nextafter nextafterl _nextafter nexttoward nexttowardf nexttowardl _o__nextafter _o_nextafter _o_nextafterf _o_nextafterl _o_nexttoward _o_nexttowardf _o_nexttowardl _o__nextafterf	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll api-ms-win-crt-math-l1-1-0.dll	DLLExport	apiref	nextafter _nextafter nextafterf nextafterl _nextafterf math/nextafter math/nextafterf math/nextafterl nexttoward nexttowardf nexttowardl math/nexttoward math/nexttowardf math/nexttowardl	_nextafter function nextafter function _nextafterf function nextafterf function nextafterl function nexttoward function nexttowardf function nexttowardl function

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

Returns the next representable floating-point value.

Syntax

double nextafter( double x, double y );
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 */

#define nextafter(X, Y) // Requires C11 or higher

double nexttoward( double x, long double y );
float nexttowardf( float x, long double y );
long double nexttowardl( long double x, long double y );

#define nexttoward(X, Y) // Requires C11 or higher

float nextafter( float x, float y ); /* C++ only, requires <cmath> */
long double nextafter( long double x, long double y ); /* C++ only, requires <cmath> */

float nexttoward( float x, long double y ); /* C++ only, requires <cmath> */
long double nexttoward( long double x, long double y ); /* C++ only, requires <cmath> */

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 and y are equal, the function returns y, converted to the return type, with no exception triggered. If x isn't 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, unless you're using the <tgmath.h> macro to call this function, nextafter and nexttoward always return double.

If you use the nextafter or nexttowardmacro from <tgmath.h>, the type of the argument determines which version of the function is selected. See Type-generic math for details.

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

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

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>
nextafter macro, nexttoward macro	<tgmath.h>

For more compatibility information, see Compatibility.

See also

Math and floating-point support
isnan, _isnan, _isnanf