import newlib-2000-02-17 snapshot

newlib/libm/math/ef_acosh.c

@@ -0,0 +1,53 @@
+/* ef_acosh.c -- float version of e_acosh.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ *
+ */
+
+#include "fdlibm.h"
+
+#ifdef __STDC__
+static const float 
+#else
+static float 
+#endif
+one	= 1.0,
+ln2	= 6.9314718246e-01;  /* 0x3f317218 */
+
+#ifdef __STDC__
+	float __ieee754_acoshf(float x)
+#else
+	float __ieee754_acoshf(x)
+	float x;
+#endif
+{	
+	float t;
+	__int32_t hx;
+	GET_FLOAT_WORD(hx,x);
+	if(hx<0x3f800000) {		/* x < 1 */
+	    return (x-x)/(x-x);
+	} else if(hx >=0x4d800000) {	/* x > 2**28 */
+	    if(hx >=0x7f800000) {	/* x is inf of NaN */
+	        return x+x;
+	    } else 
+		return __ieee754_logf(x)+ln2;	/* acosh(huge)=log(2x) */
+	} else if (hx==0x3f800000) {
+	    return 0.0;			/* acosh(1) = 0 */
+	} else if (hx > 0x40000000) {	/* 2**28 > x > 2 */
+	    t=x*x;
+	    return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one)));
+	} else {			/* 1<x<2 */
+	    t = x-one;
+	    return log1pf(t+__ieee754_sqrtf((float)2.0*t+t*t));
+	}
+}