www.pudn.com > 文件恢复及修补 C 语言源程序.zip > TANH.C

 
/*********************************************************** 
 *               The TULSA IBM C BOARD                     * 
 *                   918-664-8737                          * 
 *             300/1200 XMODEM, 24 Hours                   * 
 **********************************************************/ 
 
#include "math.h" 
 
#define P0 -0.16134119023996228053e+4 
#define P1 -0.99225929672236083313e+2 
#define P2 -0.96437492777225469787e+0 
#define Q0 +0.48402357071988688686e+4 
#define Q1 +0.22337720718962312926e+4 
#define Q2 +0.11274474380534949335e+3 
 
#define gP(g) (((P2*g P1)*g P0)*g) 
#define Q(g) (((g Q2)*g Q1)*g Q0) 
 
double tanh(x) 
double x; 
{ 
        double f,g,r; 
 
        f = fabs(x); 
        if (f > 25.3) 
                r = 1.0; 
        else if (f > 0.54930614433405484570) { 
                r = 0.5 - 1.0/(exp(f+f)+1.0); 
                r += r; 
        } else if (f < 2.3e-10) 
                r = f; 
        else { 
                g = f*f; 
                r = f + f* 
                        (gP(g) 
                        /Q(g)); 
        } 
        if (x < 0.0) 
                r = -r; 
        return r; 
}