rename libc to libjehanne; improve libposix

This is to avoid conflicts between standards' assumptions and Jehanne's choices

sys/src/lib/jehanne/port/sin.c

@@ -0,0 +1,77 @@
+/*
+ * This file is part of the UCB release of Plan 9. It is subject to the license
+ * terms in the LICENSE file found in the top-level directory of this
+ * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
+ * part of the UCB release of Plan 9, including this file, may be copied,
+ * modified, propagated, or distributed except according to the terms contained
+ * in the LICENSE file.
+ */
+
+/*
+	C program for floating point sin/cos.
+	Calls modf.
+	There are no error exits.
+	Coefficients are #3370 from Hart & Cheney (18.80D).
+*/
+
+#include <u.h>
+#include <libc.h>
+
+#define p0      .1357884097877375669092680e8
+#define p1     -.4942908100902844161158627e7
+#define p2      .4401030535375266501944918e6
+#define p3     -.1384727249982452873054457e5
+#define p4      .1459688406665768722226959e3
+#define q0      .8644558652922534429915149e7
+#define q1      .4081792252343299749395779e6
+#define q2      .9463096101538208180571257e4
+#define q3      .1326534908786136358911494e3
+
+static
+double
+sinus(double arg, int quad)
+{
+	double e, f, ysq, x, y, temp1, temp2;
+	int k;
+
+	x = arg;
+	if(x < 0) {
+		x = -x;
+		quad += 2;
+	}
+	x *= 1/PIO2;	/* underflow? */
+	if(x > 32764) {
+		y = jehanne_modf(x, &e);
+		e += quad;
+		jehanne_modf(0.25*e, &f);
+		quad = e - 4*f;
+	} else {
+		k = x;
+		y = x - k;
+		quad += k;
+		quad &= 3;
+	}
+	if(quad & 1)
+		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;
+}
+
+double
+jehanne_cos(double arg)
+{
+	if(arg < 0)
+		arg = -arg;
+	return sinus(arg, 1);
+}
+
+double
+jehanne_sin(double arg)
+{
+	return sinus(arg, 0);
+}