tinytrig.h

CD_高级PALM编程

/********************************************************************
* FILE:				TinyTrig.h
*
* DESCRIPTION:	Header file for Tiny Trig functions library.
*
* VERSION:		1.0
**********************************************************************/

// NOTE: CHANGE THESE THREE VALUES TO CHANGE THE LIBRARY ACCURACY
// The inverse trig functions accuracy cannot be improved because
// they use table lookup methods, not approximation equations.

#define		TT_MIN_VALUE				1.0e-6
#define		TT_MAX_VALUE				1.0e+6
#define		TT_ACCURACY					1.0e-6

// Other constants that define various Tiny trig limits

#define		TAN_MIN_VALUE				-552.0		// -89.9 degrees
#define		TAN_MAX_VALUE				+552.0		// +89.9 degrees
#define		POS_INFINITY					1.2e+38	// Float max
#define		NEG_INFINITY					3.4e-38	// Float min

// Plain old numeric constants and conversion factors

#define 		PI								3.14159265358979311600e+00
#define		TWO_PI						2.0 * PI
#define		HALF_PI						PI / 2.0

// The lookup table constants: size, scaling, and accuracy

#define		TRIG_TAB_SIZE				108
#define		SCALE_FACTOR					1.0e+5
#define		TT_TAB_ACCURACY			1.0e-4

// External function prototypes

double 		_sqrt ( double x );			// Square root of x
double		_abs  ( double x );			// absolute value

double 		_sin    ( double x );			// Sine of x using power series
double 		_cos   ( double x );			// Cosine of x	
double 		_tan   ( double x );			// Tangent of x
	
double 		_asin ( double x );			// Arc sine of x 
double 		_acos ( double x );			// Arc cosine of x 
double 		_atan ( double x );			// Arc tangent of x 

double		_sin2 ( double x );			// Sine of x using table lookup
double		_cos2 ( double x );			// Cosine of x using table lookup
double 		_tan2   ( double x );			// Tangent of x using table lookup

// Internal function prototypes for non-Starter functions
// Check their definitions in the source code for parameter definitions

static double		TTLookup ( double x,  UInt32 lkupTab [ TRIG_TAB_SIZE ], UInt32 rsltTab [ TRIG_TAB_SIZE ] );
static UInt8 		SearchTable ( UInt32 table [ TRIG_TAB_SIZE ], UInt32 value );
static double		ScaleNearZero ( double x, double scale );