Inside Macintosh: PowerPC Numerics / Part 2 - The PowerPC Numerics C Implementation

Chapter 8 - Environmental Control Functions

This chapter describes how to control the floating-point environment using functions defined in MathLib.

As described in Chapter 4, "Environmental Controls," the rounding direction and the exception flags are the parts of the environment that you can access. You can test and change the rounding direction, and you can test, set, and clear the exceptions flags. You may also save and restore both the rounding direction and exception flags together as a single entity. This chapter describes the functions that perform these tasks. For the definitions of rounding direction and exception flags, see Chapter 4.

Read this chapter to learn how to access and manipulate the floating-point environment in the C language. All of the environmental control function declarations appear in the file fenv.h.

IMPORTANT

If your compiler supports the environmental access switch described in Appendix D, "FPCE Recommendations for Compilers," the switch must be turned on in the program before you use any of the functions described in this chapter.

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Chapter Contents

Controlling the Rounding Direction

Controlling the Exception Flags

Accessing the Floating-Point Environment

Environmental Controls Summary

C Summary

Constants

Rounding Direction Modes

Floating-Point Exception Flags

Data Types

Environment Access Routines

Controlling the Rounding Direction

Controlling the Exception Flags

Accessing the Floating-Point Environment