# nextafter(3) [netbsd man page]

```NEXTAFTER(3)						   BSD Library Functions Manual 					      NEXTAFTER(3)

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

LIBRARY
Math Library (libm, -lm)

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);

DESCRIPTION
The nextafter(), nextafterf(), and nextafterl() functions return the next machine representable number from x in direction of y.  In other
words, if y is less than x, the functions return the largest representable floating-point number less than x.  When x equals y, the value of
y is returned.  The three functions differ only in the type of the return value and x.

The nexttoward() function is equivalent to the nextafter() family of functions with two exceptions:

1.	The second parameter has a type long double.

2.	The return value is y converted to the type of the function, provided that x equals y.

RETURN VALUES
Upon successful completion, the described functions return the next representable floating-point value as described above.  If x is finite
but an overflow would occur, a range error follows and the functions return +-HUGE_VAL, +-HUGE_VALF, or +-HUGE_VALL with the same sign as x.
When either x or y is NaN, a NaN is returned.  When x is not y but the function value is subnormal, zero, or underflows, a range error
occurs, and either 0.0 or the correct function value (if representable) is returned.

math(3)

STANDARDS
The described functions conform to ISO/IEC 9899:1999 (``ISO C99'').

BSD								September 18, 2011							       BSD```

## Check Out this Related Man Page

```nextafter(3M)						  Mathematical Library Functions					     nextafter(3M)

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

SYNOPSIS
cc [ flag... ] file... -lm [ library... ]
#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 compute the next representable floating-point value following x in the direction
of y. Thus, if y is less than x, nextafter() returns the  largest  representable  floating-point  number  less  than  x.  The  nextafter(),
nextafterf(), and nextafterl() functions return y if x equals y.

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

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

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

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

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

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

ERRORS
These functions will fail if:

Range Error     The correct value overflows.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the overflow floating-point exception is raised.

The nextafter() function sets errno to ERANGE if the correct value would overflow.

Range Error     The correct value underflows.

If the integer expression (math_errhandling & MATH_ERREXCEPT)  is  non-zero,  the  underflow  floating-point  exception	is
raised.

USAGE
An  application	wanting  to  check  for  exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if
fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception  has  been  raised.  An  application  should
either examine the return value or check the floating point exception flags to detect exceptions.

An  application	can  also  set	errno  to  0  before  calling  nextafter().  On  return,  if errno is non-zero, an error has occurred. The
nextafterf(), nextafterl(). nexttoward(), nexttowardf(), and nexttowardl() functions do not set errno.

ATTRIBUTES
See attributes(5) for descriptions of the following attributes:

+-----------------------------+-----------------------------+
|      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
+-----------------------------+-----------------------------+
|Interface Stability	     |Standard			   |
+-----------------------------+-----------------------------+
|MT-Level		     |MT-Safe			   |
+-----------------------------+-----------------------------+