1 files changed, 139 insertions, 0 deletions
diff --git a/src/pkg/big/int.go b/src/pkg/big/int.go
new file mode 100644
index 000000000..3e6bbd15e
--- /dev/null
+++ b/src/pkg/big/int.go
@@ -0,0 +1,139 @@
+// 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.
+
+// This file implements signed multi-precision integers.
+
+package big
+
+// An Int represents a signed multi-precision integer.
+// The zero value for an Int represents the value 0.
+type Int struct {
+	neg bool;  // sign
+	abs []Word;  // absolute value of the integer
+}
+
+
+// New sets z to x.
+func (z *Int) New(x int64) *Int {
+	z.neg = false;
+	if x < 0 {
+		z.neg = true;
+		x = -x;
+	}
+	z.abs = newN(z.abs, uint64(x));
+	return z;
+}
+
+
+// Set sets z to x.
+func (z *Int) Set(x *Int) *Int {
+	z.neg = x.neg;
+	z.abs = setN(z.abs, x.abs);
+	return z;
+}
+
+
+// Add computes z = x+y.
+func (z *Int) Add(x, y *Int) *Int {
+	if x.neg == y.neg {
+		// x + y == x + y
+		// (-x) + (-y) == -(x + y)
+		z.neg = x.neg;
+		z.abs = addNN(z.abs, x.abs, y.abs);
+	} else {
+		// x + (-y) == x - y == -(y - x)
+		// (-x) + y == y - x == -(x - y)
+		if cmpNN(x.abs, y.abs) >= 0 {
+			z.neg = x.neg;
+			z.abs = subNN(z.abs, x.abs, y.abs);
+		} else {
+			z.neg = !x.neg;
+			z.abs = subNN(z.abs, y.abs, x.abs);
+		}
+	}
+	if len(z.abs) == 0 {
+		z.neg = false;  // 0 has no sign
+	}
+	return z
+}
+
+
+// Sub computes z = x-y.
+func (z *Int) Sub(x, y *Int) *Int {
+	if x.neg != y.neg {
+		// x - (-y) == x + y
+		// (-x) - y == -(x + y)
+		z.neg = x.neg;
+		z.abs = addNN(z.abs, x.abs, y.abs);
+	} else {
+		// x - y == x - y == -(y - x)
+		// (-x) - (-y) == y - x == -(x - y)
+		if cmpNN(x.abs, y.abs) >= 0 {
+			z.neg = x.neg;
+			z.abs = subNN(z.abs, x.abs, y.abs);
+		} else {
+			z.neg = !x.neg;
+			z.abs = subNN(z.abs, y.abs, x.abs);
+		}
+	}
+	if len(z.abs) == 0 {
+		z.neg = false;  // 0 has no sign
+	}
+	return z
+}
+
+
+// Mul computes z = x*y.
+func (z *Int) Mul(x, y *Int) *Int {
+	// x * y == x * y
+	// x * (-y) == -(x * y)
+	// (-x) * y == -(x * y)
+	// (-x) * (-y) == x * y
+	z.neg = x.neg != y.neg;
+	z.abs = mulNN(z.abs, x.abs, y.abs);
+	return z
+}
+
+
+// Neg computes z = -x.
+func (z *Int) Neg(x *Int) *Int {
+	z.neg = len(x.abs) > 0 && !x.neg;  // 0 has no sign
+	z.abs = setN(z.abs, x.abs);
+	return z;
+}
+
+
+// CmpInt compares x and y. The result is an int value that is
+//
+//   <  0 if x <  y
+//   == 0 if x == y
+//   >  0 if x >  y
+//
+func CmpInt(x, y *Int) (r int) {
+	// x cmp y == x cmp y
+	// x cmp (-y) == x
+	// (-x) cmp y == y
+	// (-x) cmp (-y) == -(x cmp y)
+	switch {
+	case x.neg == y.neg:
+		r = cmpNN(x.abs, y.abs);
+		if x.neg {
+			r = -r;
+		}
+	case x.neg:
+		r = -1;
+	default:
+		r = 1;
+	}
+	return;
+}
+
+
+func (x *Int) String() string {
+	s := "";
+	if x.neg {
+		s = "-";
+	}
+	return s + stringN(x.abs, 10);
+}