Initial revision

lang/cem/libcc/math/sqrt.c

@@ -0,0 +1,41 @@
+/*
+ * (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 <errno.h>
+
+extern int errno;
+
+#define NITER	5
+
+double
+sqrt(x)
+	double x;
+{
+	extern double frexp(), ldexp();
+	int exponent;
+	double val;
+
+	if (x <= 0) {
+		if (x < 0) errno = EDOM;
+		return 0;
+	}
+
+	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;
+}