# GENWiki

Premier IT Outsourcing and Support Services within the UK

### Site Tools

man:nextup

NEXTUP(3) Linux Programmer's Manual NEXTUP(3)

NAME

```     nextup,  nextupf, nextupl, nextdown, nextdownf, nextdownl - return next
floating-point number toward positive/negative infinity```

SYNOPSIS

```     #define _GNU_SOURCE     /* See feature_test_macros(7) */
#include <math.h>```
```     double nextup(double x);
float nextupf(float x);
long double nextupl(long double x);```
```     double nextdown(double x);
float nextdownf(float x);
long double nextdownl(long double x);```
`     Link with -lm.`

DESCRIPTION

```     The nextup(), nextupf(), and nextupl() functions return the next repre-
sentable floating-point number greater than x.```
```     If x is the smallest representable negative number in the corresponding
type, these functions return -0.  If x is 0, the returned value is  the
smallest representable positive number of the corresponding type.```
```     If x is positive infinity, the returned value is positive infinity.  If
x is negative infinity, the returned value is the largest representable
finite negative number of the corresponding type.```
`     If x is Nan, the returned value is NaN.`
```     The value returned by nextdown(x) is -nextup(-x), and similarly for the
other types.```

RETURN VALUE

`     See DESCRIPTION.`

VERSIONS

`     These functions first appeared in glibc in version 2.24.`

ATTRIBUTES

```     For  an  explanation  of  the  terms  used   in   this   section,   see
attributes(7).```
```     +-------------------------------------+---------------+---------+
|Interface                            | Attribute     | Value   |
+-------------------------------------+---------------+---------+
|nextup(), nextupf(), nextupl(),      | Thread safety | MT-Safe |
|nextdown(), nextdownf(), nextdownl() |               |         |
+-------------------------------------+---------------+---------+```

CONFORMING TO

```     These functions are described in  IEEE  Std  754-2008  -  Standard  for
Floating-Point Arithmetic and ISO/IEC TS 18661.```

`     nearbyint(3), nextafter(3)`

COLOPHON

```     This  page  is  part of release 4.16 of the Linux man-pages project.  A
description of the project, information about reporting bugs,  and  the
latest     version     of     this    page,    can    be    found    at
https://www.kernel.org/doc/man-pages/.```

GNU 2017-09-15 NEXTUP(3)