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

NAME

```     fpclassify, isfinite, isnormal, isnan, isinf - floating-point classifi-
cation macros```

SYNOPSIS

`     #include <math.h>`
`     int fpclassify(x);`
`     int isfinite(x);`
`     int isnormal(x);`
`     int isnan(x);`
`     int isinf(x);`
`     Link with -lm.`
` Feature Test Macro Requirements for glibc (see feature_test_macros(7)):`
```     fpclassify(), isfinite(), isnormal():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
isnan():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| _XOPEN_SOURCE
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
isinf():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE```

DESCRIPTION

```     Floating point numbers can have special values,  such  as  infinite  or
NaN.   With  the  macro  fpclassify(x) you can find out what type x is.
The macro takes any floating-point expression as argument.  The  result
is one of the following values:```
`     FP_NAN        x is "Not a Number".`
`     FP_INFINITE   x is either positive infinity or negative infinity.`
`     FP_ZERO       x is zero.`
`     FP_SUBNORMAL  x is too small to be represented in normalized format.`
```     FP_NORMAL     if nothing of the above is correct then it must be a nor-
mal floating-point number.```
`     The other macros provide a short answer to some standard questions.`
```     isfinite(x)   returns a nonzero value if
(fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)```
`     isnormal(x)   returns a nonzero value if (fpclassify(x) == FP_NORMAL)`
`     isnan(x)      returns a nonzero value if (fpclassify(x) == FP_NAN)`
```     isinf(x)      returns 1 if x is positive infinity, and -1 if x is nega-
tive infinity.```

ATTRIBUTES

```     For  an  explanation  of  the  terms  used   in   this   section,   see
attributes(7).```
```     allbox; lbw28 lb lb l l l.  Interface Attribute Value T{ fpclassify(),
isfinite(), isnormal(), isnan(), isinf() T}   Thread safety  MT-Safe```

CONFORMING TO

`     POSIX.1-2001, POSIX.1-2008, C99.`
```     For isinf(), the standards merely say that the return value is  nonzero
if and only if the argument has an infinite value.```

NOTES

```     In  glibc  2.01 and earlier, isinf() returns a nonzero value (actually:
1) if x is positive infinity or negative infinity.  (This is  all  that
C99 requires.)```

`     finite(3), INFINITY(3), isgreater(3), signbit(3)`
```     This  page  is  part of release 4.16 of the Linux man-pages project.  A
`                                2017-09-15                     FPCLASSIFY(3)`