1 files changed, 45 insertions, 0 deletions
diff --git a/src/math/e_acoshf.c b/src/math/e_acoshf.c
new file mode 100644
index 00000000..b7f1df69
--- /dev/null
+++ b/src/math/e_acoshf.c
@@ -0,0 +1,45 @@
+/* e_acoshf.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 <math.h>
+#include "math_private.h"
+
+static const float
+one     = 1.0,
+ln2     = 6.9314718246e-01;  /* 0x3f317218 */
+
+float
+acoshf(float x)
+{
+        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 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 logf((float)2.0*x-one/(x+sqrtf(t-one)));
+        } else {                        /* 1<x<2 */
+            t = x-one;
+            return log1pf(t+sqrtf((float)2.0*t+t*t));
+        }
+}