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## NAME

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

```

## 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(): _BSD_SOURCE || _SVID_SOURCE
isinf(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
_ISOC99_SOURCE; cc -std=c99
isinff(), isinfl(): _BSD_SOURCE || _SVID_SOURCE
isnan(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE ||
_ISOC99_SOURCE; cc -std=c99
isnanf(), isnanl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600

```

## DESCRIPTION

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

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

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

```

## 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).

```

```       fpclassify(3)
```       This  page  is  part of release 3.24 of the Linux man-pages project.  A