1 files changed, 64 insertions, 0 deletions
diff --git a/src/lib/math/sqrt.go b/src/lib/math/sqrt.go
new file mode 100644
index 000000000..8209a3ac4
--- /dev/null
+++ b/src/lib/math/sqrt.go
@@ -0,0 +1,64 @@
+// 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 sqrt
+
+import		sys "sys"
+export		sqrt
+
+/*
+	sqrt returns the square root of its floating
+	point argument. Newton's method.
+
+	calls frexp
+*/
+
+func
+sqrt(arg double) double
+{
+	var x, temp double;
+	var exp, i int;
+
+	if sys.isInf(arg, 1) {
+		return arg;
+	}
+
+	if arg <= 0 {
+		if arg < 0 {
+			return sys.NaN();
+		}
+		return 0;
+	}
+
+	exp,x = sys.frexp(arg);
+	for x < 0.5 {
+		x = x*2;
+		exp = exp-1;
+	}
+
+	if exp&1 != 0 {
+		x = x*2;
+		exp = exp-1;
+	}
+	temp = 0.5 * (1+x);
+
+	for exp > 60 {
+		temp = temp * double(1<<30);
+		exp = exp - 60;
+	}
+	for exp < -60 {
+		temp = temp / double(1<<30);
+		exp = exp + 60;
+	}
+	if exp >= 0 {
+		temp = temp * double(1 << (exp/2));
+	} else {
+		temp = temp / double(1 << (-exp/2));
+	}
+
+	for i=0; i<=4; i=i+1 {
+		temp = 0.5*(temp + arg/temp);
+	}
+	return temp;
+}