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c99 [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*);

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*.

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.

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.

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**.

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

ATTRIBUTE TYPE | ATTRIBUTE VALUE |

Interface Stability | Standard |

MT-Level | MT-Safe |

**feclearexcept**(3M), **fetestexcept**(3M), **math.h**(3HEAD), **attributes**(5), **standards**(5)

- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- ERRORS
- USAGE
- ATTRIBUTES
- SEE ALSO

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Time: 02:39:32 GMT, October 02, 2010