Initial revision

lib/math/sqrt.c

@@ -0,0 +1,43 @@
+/*
+ * (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
+ * See the copyright notice in the ACK home directory, in the file "Copyright".
+ *
+ * Author: Ceriel J.H. Jacobs
+ */
+/* $Header$ */
+
+#include	<math.h>
+#include	<float.h>
+#include	<errno.h>
+
+#define NITER	5
+
+double
+sqrt(double x)
+{
+	int exponent;
+	double val;
+
+	if (__IsNan(x)) {
+		errno = EDOM;
+		return x;
+	}
+	if (x <= 0) {
+		if (x < 0) errno = EDOM;
+		return 0;
+	}
+
+	if (x > DBL_MAX) return x;	/* for infinity */
+
+	val = frexp(x, &exponent);
+	if (exponent & 1) {
+		exponent--;
+		val *= 2;
+	}
+	val = ldexp(val + 1.0, exponent/2 - 1);
+	/* was: val = (val + 1.0)/2.0; val = ldexp(val, exponent/2); */
+	for (exponent = NITER - 1; exponent >= 0; exponent--) {
+		val = (val + x / val) / 2.0;
+	}
+	return val;
+}