From 11da511c784eca003deb90c23570f0873954e0de Mon Sep 17 00:00:00 2001
From: Duncan Wilkie <antigravityd@gmail.com>
Date: Sat, 18 Nov 2023 06:11:09 -0600
Subject: Initial commit.

---
 ic-reals-6.3/math-lib/atan_R.c~ | 135 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 135 insertions(+)
 create mode 100644 ic-reals-6.3/math-lib/atan_R.c~

(limited to 'ic-reals-6.3/math-lib/atan_R.c~')

diff --git a/ic-reals-6.3/math-lib/atan_R.c~ b/ic-reals-6.3/math-lib/atan_R.c~
new file mode 100644
index 0000000..a6c1154
--- /dev/null
+++ b/ic-reals-6.3/math-lib/atan_R.c~
@@ -0,0 +1,135 @@
+/*
+ * Copyright (C) 2000, Imperial College
+ *
+ * This file is part of the Imperial College Exact Real Arithmetic Library.
+ * See the copyright notice included in the distribution for conditions
+ * of use.
+ */
+
+#include <stdio.h>
+#include "real.h"
+#include "real-impl.h"
+#include "math-lib.h"
+
+static TenXY *nextTensor(Real, Real, int);
+static void atanInside();
+static void atanPositive();
+static void atanNegative();
+
+Real
+atan_R(Real x)
+{
+	Real u, v, w;
+	Bool xLtEq1, xGtEqNeg1, xLtEq1_and_GtEqNeg1;
+	static int doneInit = 0;
+
+	if (!doneInit) {
+		registerForceFunc(atanInside, "atanInside", 2);
+		registerForceFunc(atanPositive, "atanPositive", 2);
+		registerForceFunc(atanNegative, "atanNegative", 2);
+		doneInit++;
+	}
+
+	xLtEq1 = ltEq_R_QInt(x, 1, 1);
+	xGtEqNeg1 = gtEq_R_QInt(x, -1, 1);
+	xLtEq1_and_GtEqNeg1 = and_B_B(xLtEq1, xGtEqNeg1);
+		
+	u = (Real) allocCls(atanInside, (void *) x);
+	u->cls.tag.isSigned = TRUE;
+	v = (Real) allocCls(atanPositive, (void *) x);
+	v->cls.tag.isSigned = TRUE;
+	w = (Real) allocCls(atanNegative, (void *) x);
+	w->cls.tag.isSigned = TRUE;
+	
+	if (DAVINCI) {
+		beginGraphUpdate();
+		newEdgeToOnlyChild(u, x);
+		newEdgeToOnlyChild(v, x);
+		newEdgeToOnlyChild(w, x);
+		endGraphUpdate();
+	}
+
+	/*
+	 * The order of the tests in the alt is not semantically
+	 * significant. The tests are applied in order, so there is a
+	 * very modest performance improvement by putting the -1,1 tests
+	 * before the 999/1000,-999/1000 tests.  Also there is a very
+	 * small win by doing the negative test before the positive test.
+	 */
+	return realIf(3,
+		xLtEq1_and_GtEqNeg1,			u,
+		gtEq_R_QInt(x, 999, 1000),		v,
+		ltEq_R_QInt(x, -999, 1000),		w);
+}
+
+static TenXY *
+nextTensor(Real x, Real y, int n)
+{
+    return (TenXY *) tensor_Int(x, y, 2*n+1, 1, -1, -(2*n+1),
+					2*n+1, 2*n+1, 2*n+1, 2*n+1);
+}
+
+static void
+atanInside()
+{
+	Cls *cls, *newCls;
+	Real x, atan_x;
+	ClsData *data;
+	void stdTensorCont();
+
+	cls = (Cls *) POP;
+	x = (Real) cls->userData;
+	
+	if ((data = (ClsData *) malloc(sizeof(ClsData))) == NULL)
+		Error(FATAL, E_INT, "atan_R", "malloc failed");
+
+	data->n = 1;
+	data->x = x;
+	data->nextTensor = nextTensor;
+
+	newCls = allocCls(stdTensorCont, (void *) data);
+	newCls->tag.isSigned = FALSE;
+
+	cls->redirect = tensor_Int(x, (Real) newCls, 1, 1, 1, -1, 0, 1, 0, 1);
+
+	if (DAVINCI) {
+		beginGraphUpdate();
+		newEdgeToOnlyChild(newCls, x);
+		drawEqEdge(cls, cls->redirect);
+		endGraphUpdate();
+	}
+}
+
+/*
+ * This implements the identity:
+ *   x > 0 implies atan(x) = atan(szero * x) + \pi/4
+ */
+static void
+atanPositive()
+{
+	Cls *cls, *newCls;
+	Real x, y;
+
+	cls = (Cls *) POP;
+	x = (Real) cls->userData;
+	
+	y = atan_R(matrix_Int(x, 1, 1, -1, 1));
+	cls->redirect = add_R_R(y, div_R_Int(Pi, 4));
+}
+
+/*
+ * This implements the identity:
+ *   x < 0 implies atan(x) = atan(szero * (sneg^(-1) * x) - \pi/4
+ */
+static void
+atanNegative()
+{
+	Cls *cls, *newCls;
+	Real x, y;
+
+	cls = (Cls *) POP;
+	x = (Real) cls->userData;
+	
+	y = atan_R(matrix_Int(x, 1, -1, 1, 1));
+	cls->redirect = sub_R_R(y, div_R_Int(Pi, 4));
+}
-- 
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