From 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 12 Feb 2011 00:22:29 -0500
Subject: initial check-in, version 0.5.0

---
 src/math/s_atanf.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 src/math/s_atanf.c

(limited to 'src/math/s_atanf.c')

diff --git a/src/math/s_atanf.c b/src/math/s_atanf.c
new file mode 100644
index 00000000..03067e18
--- /dev/null
+++ b/src/math/s_atanf.c
@@ -0,0 +1,95 @@
+/* s_atanf.c -- float version of s_atan.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 atanhi[] = {
+  4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
+  7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
+  9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
+  1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
+};
+
+static const float atanlo[] = {
+  5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
+  3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
+  3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
+  7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
+};
+
+static const float aT[] = {
+  3.3333334327e-01, /* 0x3eaaaaaa */
+ -2.0000000298e-01, /* 0xbe4ccccd */
+  1.4285714924e-01, /* 0x3e124925 */
+ -1.1111110449e-01, /* 0xbde38e38 */
+  9.0908870101e-02, /* 0x3dba2e6e */
+ -7.6918758452e-02, /* 0xbd9d8795 */
+  6.6610731184e-02, /* 0x3d886b35 */
+ -5.8335702866e-02, /* 0xbd6ef16b */
+  4.9768779427e-02, /* 0x3d4bda59 */
+ -3.6531571299e-02, /* 0xbd15a221 */
+  1.6285819933e-02, /* 0x3c8569d7 */
+};
+
+        static const float
+one   = 1.0,
+huge   = 1.0e30;
+
+float
+atanf(float x)
+{
+        float w,s1,s2,z;
+        int32_t ix,hx,id;
+
+        GET_FLOAT_WORD(hx,x);
+        ix = hx&0x7fffffff;
+        if(ix>=0x50800000) {    /* if |x| >= 2^34 */
+            if(ix>0x7f800000)
+                return x+x;             /* NaN */
+            if(hx>0) return  atanhi[3]+atanlo[3];
+            else     return -atanhi[3]-atanlo[3];
+        } if (ix < 0x3ee00000) {        /* |x| < 0.4375 */
+            if (ix < 0x31000000) {      /* |x| < 2^-29 */
+                if(huge+x>one) return x;        /* raise inexact */
+            }
+            id = -1;
+        } else {
+        x = fabsf(x);
+        if (ix < 0x3f980000) {          /* |x| < 1.1875 */
+            if (ix < 0x3f300000) {      /* 7/16 <=|x|<11/16 */
+                id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
+            } else {                    /* 11/16<=|x|< 19/16 */
+                id = 1; x  = (x-one)/(x+one);
+            }
+        } else {
+            if (ix < 0x401c0000) {      /* |x| < 2.4375 */
+                id = 2; x  = (x-(float)1.5)/(one+(float)1.5*x);
+            } else {                    /* 2.4375 <= |x| < 2^66 */
+                id = 3; x  = -(float)1.0/x;
+            }
+        }}
+    /* end of argument reduction */
+        z = x*x;
+        w = z*z;
+    /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
+        s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10])))));
+        s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9]))));
+        if (id<0) return x - x*(s1+s2);
+        else {
+            z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
+            return (hx<0)? -z:z;
+        }
+}
-- 
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