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

IEEE Standard for Binary Floating-Point Arithmetic (ANSI/IEEE Standards 754-1985 and 854-1987).

List of Numerical Manipulation Services and Subroutines Overview in AIX Version 4.3 General Programming Concepts: Writing and Debugging Programs.