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+/* origin: OpenBSD /usr/src/lib/libm/src/s_catanf.c */
+/*
+ * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * Complex circular arc tangent
+ *
+ *
+ * SYNOPSIS:
+ *
+ * float complex catanf();
+ * float complex z, w;
+ *
+ * w = catanf( z );
+ *
+ *
+ * DESCRIPTION:
+ *
+ * If
+ * z = x + iy,
+ *
+ * then
+ * 1 ( 2x )
+ * Re w = - arctan(-----------) + k PI
+ * 2 ( 2 2)
+ * (1 - x - y )
+ *
+ * ( 2 2)
+ * 1 (x + (y+1) )
+ * Im w = - log(------------)
+ * 4 ( 2 2)
+ * (x + (y-1) )
+ *
+ * Where k is an arbitrary integer.
+ *
+ *
+ * ACCURACY:
+ *
+ * Relative error:
+ * arithmetic domain # trials peak rms
+ * IEEE -10,+10 30000 2.3e-6 5.2e-8
+ */
+
+#include "complex_impl.h"
+
+#define MAXNUMF 1.0e38F
+
+static const double DP1 = 3.140625;
+static const double DP2 = 9.67502593994140625E-4;
+static const double DP3 = 1.509957990978376432E-7;
+
+static const float float_pi = M_PI;
+
+static float _redupif(float xx)
+{
+ float x, t;
+ long i;
+
+ x = xx;
+ t = x/float_pi;
+ if (t >= 0.0f)
+ t += 0.5f;
+ else
+ t -= 0.5f;
+
+ i = t; /* the multiple */
+ t = i;
+ t = ((x - t * DP1) - t * DP2) - t * DP3;
+ return t;
+}
+
+float complex catanf(float complex z)
+{
+ float complex w;
+ float a, t, x, x2, y;
+
+ x = crealf(z);
+ y = cimagf(z);
+
+ x2 = x * x;
+ a = 1.0f - x2 - (y * y);
+
+ t = 0.5f * atan2f(2.0f * x, a);
+ w = _redupif(t);
+
+ t = y - 1.0f;
+ a = x2 + (t * t);
+
+ t = y + 1.0f;
+ a = (x2 + (t * t))/a;
+ w = CMPLXF(w, 0.25f * logf(a));
+ return w;
+}