Home | History | Annotate | Download | only in src
      1 /* e_coshf.c -- float version of e_cosh.c.
      2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian (at) cygnus.com.
      3  */
      4 
      5 /*
      6  * ====================================================
      7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
      8  *
      9  * Developed at SunPro, a Sun Microsystems, Inc. business.
     10  * Permission to use, copy, modify, and distribute this
     11  * software is freely granted, provided that this notice
     12  * is preserved.
     13  * ====================================================
     14  */
     15 
     16 #ifndef lint
     17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_coshf.c,v 1.7 2005/11/13 00:08:23 bde Exp $";
     18 #endif
     19 
     20 #include "math.h"
     21 #include "math_private.h"
     22 
     23 static const float one = 1.0, half=0.5, huge = 1.0e30;
     24 
     25 float
     26 __ieee754_coshf(float x)
     27 {
     28 	float t,w;
     29 	int32_t ix;
     30 
     31 	GET_FLOAT_WORD(ix,x);
     32 	ix &= 0x7fffffff;
     33 
     34     /* x is INF or NaN */
     35 	if(ix>=0x7f800000) return x*x;
     36 
     37     /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
     38 	if(ix<0x3eb17218) {
     39 	    t = expm1f(fabsf(x));
     40 	    w = one+t;
     41 	    if (ix<0x39800000) return one;	/* cosh(tiny) = 1 */
     42 	    return one+(t*t)/(w+w);
     43 	}
     44 
     45     /* |x| in [0.5*ln2,9], return (exp(|x|)+1/exp(|x|))/2; */
     46 	if (ix < 0x41100000) {
     47 		t = __ieee754_expf(fabsf(x));
     48 		return half*t+half/t;
     49 	}
     50 
     51     /* |x| in [9, log(maxfloat)] return half*exp(|x|) */
     52 	if (ix < 0x42b17217)  return half*__ieee754_expf(fabsf(x));
     53 
     54     /* |x| in [log(maxfloat), overflowthresold] */
     55 	if (ix<=0x42b2d4fc) {
     56 	    w = __ieee754_expf(half*fabsf(x));
     57 	    t = half*w;
     58 	    return t*w;
     59 	}
     60 
     61     /* |x| > overflowthresold, cosh(x) overflow */
     62 	return huge*huge;
     63 }
     64