[C++] isinf(), isnan() & finite() odefinierade?

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



NAME
       fpclassify,  isfinite,  isnormal, isnan - floating-point classification
       macros

SYNOPSIS
       #include <math.h>

       int fpclassify(x);

       int isfinite(x);

       int isnormal(x);

       int isnan(x);

       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 fpclassify(x) you can find out what type x is. The
       macro takes any floating-point  expression  as  argument.   The  result
       takes one of the following values:

       FP_NAN x is "Not a Number".

       FP_INFINITE
              x is either plus or minus 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 that it must be a normal
              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 a nonzero value if (fpclassify(x) == FP_INFINITE)

NOTE
       On systems conforming to BSD 4.3, isinf() will return 1  for  positive,
       and -1 for negative infinity.

CONFORMING TO
       C99

SEE ALSO
       finite(3), INFINITY(3), isgreater(3)




                                  2004-10-31                     fpclassify(3)