NAME
fpclassify, isfinite, isnormal, isnan, isinf - floating-point
classification macros
SYNOPSIS
#include <math.h>
I int fpclassify( x );
I int isfinite( x );
I int isnormal( x );
I int isnan( x );
I int isinf( x );
Compile with
-std=c99; link with
-lm.
DESCRIPTION
Floating point numbers can have special values, such as
infinite or NaN.
With the macro
I 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 plus or minus infinity.
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
normal floating-point number.
The other macros provide a short answer to some standard questions.
I isfinite( x )
returns a non-zero value if
(fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
I isnormal( x )
returns a non-zero value if
(fpclassify(x) == FP_NORMAL)
I isnan( x )
returns a non-zero value if
(fpclassify(x) == FP_NAN)
I isinf( x )
returns 1 if
x
is positive infinity, and -1 if
x
is negative infinity.
CONFORMING TO
C99
NOTES
In glibc 2.01 and earlier,
R isinf ()
returns a non-zero value (actually: 1) if
x
is an infinity (positive or negative).
(This is all that C99 requires.)
SEE ALSO
ČLÁNKY DO MAILU