1 files changed, 39 insertions, 0 deletions
diff --git a/src/pkg/exp/eval/util.go b/src/pkg/exp/eval/util.go
new file mode 100644
index 000000000..9cdf23722
--- /dev/null
+++ b/src/pkg/exp/eval/util.go
@@ -0,0 +1,39 @@
+// 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 eval
+
+import (
+	"bignum";
+)
+
+// TODO(austin): Maybe add to bignum in more general form
+func ratToString(rat *bignum.Rational) string {
+	n, dnat := rat.Value();
+	d := bignum.MakeInt(false, dnat);
+	w, frac := n.QuoRem(d);
+	out := w.String();
+	if frac.IsZero() {
+		return out;
+	}
+
+	r := frac.Abs();
+	r = r.Mul(bignum.Nat(1e6));
+	dec, tail := r.DivMod(dnat);
+	// Round last digit
+	if tail.Cmp(dnat.Div(bignum.Nat(2))) >= 0 {
+		dec = dec.Add(bignum.Nat(1));
+	}
+	// Strip zeros
+	ten := bignum.Nat(10);
+	for !dec.IsZero() {
+		dec2, r2 := dec.DivMod(ten);
+		if !r2.IsZero() {
+			break;
+		}
+		dec = dec2;
+	}
+	out += "." + dec.String();
+	return out;
+}