# nexttowardf(3) [posix man page]

```NEXTAFTER(P)						     POSIX Programmer's Manual						      NEXTAFTER(P)

NAME
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl - next representable floating-point number

SYNOPSIS
#include <math.h>

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

DESCRIPTION
The  nextafter(),  nextafterf(),  and  nextafterl()  functions shall compute the next representable floating-point value following x in the
direction of y.	Thus, if y is less than x, nextafter() shall return the largest representable  floating-point  number  less  than  x.  The
nextafter(), nextafterf(), and nextafterl() functions shall return y if x equals y.

The  nexttoward(),  nexttowardf(),  and nexttowardl() functions shall be equivalent to the corresponding nextafter() functions, except that
the second parameter shall have type long double and the functions shall return y converted to the type of the function if x equals y.

An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT)  before  calling  these
functions.   On	return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error
has occurred.

RETURN VALUE
Upon successful completion, these functions shall return the next representable floating-point value following x in the direction of y.

If x== y, y (of the type x) shall be returned.

If x is finite and the correct function value would overflow, a range error shall occur and +-HUGE_VAL, +-HUGE_VALF, and +-HUGE_VALL  (with
the same sign as x) shall be returned as appropriate for the return type of the function.

If x or y is NaN, a NaN shall be returned.

If x!= y and the correct function value is subnormal, zero, or underflows, a range error shall occur, and either the correct function value
(if representable) or 0.0 shall be returned.

ERRORS
These functions shall fail if:

Range Error
The correct value overflows.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set  to  [ERANGE].  If  the  integer	expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.

Range Error
The correct value is subnormal or underflows.

If  the	integer  expression  (math_errhandling	&  MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

The following sections are informative.

EXAMPLES
None.

APPLICATION USAGE
On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of  each  other,  but	at
least one of them must be non-zero.

RATIONALE
None.

FUTURE DIRECTIONS
None.

feclearexcept()	,  fetestexcept()  ,  the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for
Mathematical Functions, <math.h>

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and  the  original  IEEE
and  The  Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group						       2003							      NEXTAFTER(P)```
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