finite(3) Library Functions Manual finite(3)

# NAME¶

finite, finitef, finitel, isinf, isinff, isinfl, isnan, isnanf, isnanl - BSD floating-point classification functions

# LIBRARY¶

Math library (libm, -lm)

# SYNOPSIS¶

`#include <math.h>`
```int finite(double x);
int finitef(float x);
int finitel(long double x);```
```int isinf(double x);
int isinff(float x);
int isinfl(long double x);```
```int isnan(double x);
int isnanf(float x);
int isnanl(long double x);```

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

finite(), finitef(), finitel():

```
/* glibc >= 2.19: */ _DEFAULT_SOURCE

|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE```
```isinf():

_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE

|| /* glibc >= 2.19: */ _DEFAULT_SOURCE

|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE```

isinff(), isinfl():

```
/* glibc >= 2.19: */ _DEFAULT_SOURCE

|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE```

isnan():

```
_XOPEN_SOURCE || _ISOC99_SOURCE

|| /* glibc >= 2.19: */ _DEFAULT_SOURCE

|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE```

isnanf(), isnanl():

```
_XOPEN_SOURCE >= 600

|| /* glibc >= 2.19: */ _DEFAULT_SOURCE

|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE```

# DESCRIPTION¶

The finite(), finitef(), and finitel() functions return a nonzero value if x is neither infinite nor a "not-a-number" (NaN) value, and 0 otherwise.

The isnan(), isnanf(), and isnanl() functions return a nonzero value if x is a NaN value, and 0 otherwise.

The isinf(), isinff(), and isinfl() functions return 1 if x is positive infinity, -1 if x is negative infinity, and 0 otherwise.

# ATTRIBUTES¶

For an explanation of the terms used in this section, see attributes(7).

 Interface Attribute Value finite (), finitef (), finitel (), isinf (), isinff (), isinfl (), isnan (), isnanf (), isnanl () Thread safety MT-Safe

# NOTES¶

Note that these functions are obsolete. C99 defines macros isfinite(), isinf(), and isnan() (for all types) replacing them. Further note that the C99 isinf() has weaker guarantees on the return value. See fpclassify(3).