Technical Reference: Base Operating System and Extensions, Volume 1

class, _class, finite, isnan, or unordered Subroutines

Purpose

Determines classifications of floating-point numbers.

Libraries

IEEE Math Library (libm.a)
or System V Math Library (libmsaa.a)

Syntax

#include <math.h>
#include <float.h>

int
class( x)
double x;

#include <math.h>
#include <float.h>

int
_class( x)
double x;

#include <math.h>

int finite(x)
double x;

#include <math.h>

int isnan(x)
double x;

#include <math.h>

int unordered(x, y)
double x, y;

Description

The class subroutine, _class subroutine, finite subroutine, isnan subroutine, and unordered subroutine determine the classification of their floating-point value. The unordered subroutine determines if a floating-point comparison involving x and y would generate the IEEE floating-point unordered condition (such as whether x or y is a NaN).

The class subroutine returns an integer that represents the classification of the floating-point x parameter. Since class is a reversed key word in C++. The class subroutine can not be invoked in a C++ program. The _class subroutine is an interface for C++ program using the class subroutine. The interface and the return value for class and _class subroutines are identical. The values returned by the class subroutine are defined in the float.h header file. The return values are the following:

Since class is a reserved keyword in C++, the class subroutine cannot be invoked in a C++ program. The _class subroutine is an interface for the C++ program using the class subroutine. The interface and the return values for class and _class subroutines are identical.

The finite subroutine returns a nonzero value if the x parameter is a finite number; that is, if x is not +-, INF, NaNQ, or NaNS.

The isnan subroutine returns a nonzero value if the x parameter is an NaNS or a NaNQ. Otherwise, it returns 0.

The unordered subroutine returns a nonzero value if a floating-point comparison between x and y would be unordered. Otherwise, it returns 0.

Note: Compile any routine that uses subroutines from the libm.a library with the -lm flag. To compile the class.c file, for example, enter:

cc class.c -lm

Parameters

Error Codes

The finite, isnan, and unordered subroutines neither return errors nor set bits in the floating-point exception status, even if a parameter is an NaNS.

Implementation Specifics

These subroutines are part of Base Operating System (BOS) Runtime.

Related Information

List of Numerical Manipulation Services and Subroutines Overview in AIX 5L Version 5.1 General Programming Concepts: Writing and Debugging Programs.