_fpclass, _fpclassl

Remonter à float.h - Index

Header File

float.h

Category

Math Routines

Prototype

int _fpclass(double d);

int _fpclassl(long double ld);

Description

Returns an integer value representing the type (class) of an IEEE real for doubles. This value contains information on the floating-point class of the argument.

_fpclassl is the long double version; it takes a long double argument and returns the type (class) of an IEEE real for long doubles.

Return Value

Returns an integer value that indicates the floating-point class of its argument. The possible values, which are listed in the table below, are defined in FLOAT.H.

_FPCLASS_UNSUP	Unsupported IEEE format
_FPCLASS_SNAN	Signaling NaN
_FPCLASS_QNAN	Quiet NaN
_FPCLASS_NINF	Negative infinity
_FPCLASS_NN	Negative normalized non-zero
_FPCLASS_ND	Negative denormal
_FPCLASS_NZ	Negative zero (-0.0)
_FPCLASS_PZ	Positive zero (+0.0)
_FPCLASS_PD	Positive denormal
_FPCLASS_PN	Positive normalized non-zero
_FPCLASS_PINF	Positive infinity

Example

#include <float.h>
#include <stdio.h>

/* Compare a and b */
int compare(double a, double b)
{
  /* Only if both are finite. */
  if (_finite(a) && _finite(b)) {
    if (a < b)
      return -1;
    else if (a > b)
      return 1;
    else
      return 0;
  }
  else
  {
    /* For infinite values check the class of the numbers */
    int class_a = _fpclass(a);
    int class_b = _fpclass(b);

    /* No check the infinities and compare them */
    if (class_a == _FPCLASS_NINF) 
    {
      if (class_b == _FPCLASS_NINF)
        return 0;
      else
        return -1;
    } else if (class_a == _FPCLASS_PINF) 
    {
      if (class_b == _FPCLASS_PINF)
        return 0;
      else
        return 1;
    }
  }
  
  /* Cannot find a relationship! */
  return -1;
}

Portability

	POSIX	Win32	ANSI C	ANSI C++
_fpclass		+
_fpclassl		+