SVN=114204

src/lib/math/sin.go

@@ -0,0 +1,73 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sin
+
+import	sys "sys"
+export	sin, cos
+
+const
+(
+	p0	=  .1357884097877375669092680e8;
+	p1	= -.4942908100902844161158627e7;
+	p2	=  .4401030535375266501944918e6;
+	p3	= -.1384727249982452873054457e5;
+	p4	=  .1459688406665768722226959e3;
+	q0	=  .8644558652922534429915149e7;
+	q1	=  .4081792252343299749395779e6;
+	q2	=  .9463096101538208180571257e4;
+	q3	=  .1326534908786136358911494e3;
+        piu2	=  .6366197723675813430755350e0;	// 2/pi
+)
+
+func
+sinus(arg double, quad int) double
+{
+	var e, f, ysq, x, y, temp1, temp2 double;
+	var k long;
+
+	x = arg;
+	if(x < 0) {
+		x = -x;
+		quad = quad+2;
+	}
+	x = x * piu2;	/* underflow? */
+	if x > 32764 {
+		e,y = sys.modf(x);
+		e = e + double(quad);
+		temp1,f = sys.modf(0.25*e);
+		quad = int(e - 4*f);
+	} else {
+		k = long(x);
+		y = x - double(k);
+		quad = (quad + k) & 3;
+	}
+
+	if quad&1 != 0 {
+		y = 1-y;
+	}
+	if quad > 1 {
+		y = -y;
+	}
+
+	ysq = y*y;
+	temp1 = ((((p4*ysq+p3)*ysq+p2)*ysq+p1)*ysq+p0)*y;
+	temp2 = ((((ysq+q3)*ysq+q2)*ysq+q1)*ysq+q0);
+	return temp1/temp2;
+}
+
+func
+cos(arg double) double
+{
+	if arg < 0 {
+		arg = -arg;
+	}
+	return sinus(arg, 1);
+}
+
+func
+sin(arg double) double
+{
+	return sinus(arg, 0);
+}