big: added a few missing functions:
- sign to determine if a value is < 0, == 0, > 0
- abs to compute absolute value
- Rat.IsInt to test if a rational number is representable as an integer
R=rsc
CC=golang-dev
https://golang.org/cl/1761042
diff --git a/src/pkg/big/int.go b/src/pkg/big/int.go
index f16c0d9..e7ba402 100755
--- a/src/pkg/big/int.go
+++ b/src/pkg/big/int.go
@@ -20,6 +20,23 @@
var intOne = &Int{false, natOne}
+// Sign returns:
+//
+// -1 if x < 0
+// 0 if x == 0
+// +1 if x > 0
+//
+func (x *Int) Sign() int {
+ if len(x.abs) == 0 {
+ return 0
+ }
+ if x.neg {
+ return -1
+ }
+ return 1
+}
+
+
// SetInt64 sets z to x and returns z.
func (z *Int) SetInt64(x int64) *Int {
neg := false
@@ -47,6 +64,14 @@
}
+// Abs sets z to |x| (the absolute value of x) and returns z.
+func (z *Int) Abs(x *Int) *Int {
+ z.abs = z.abs.set(x.abs)
+ z.neg = false
+ return z
+}
+
+
// Neg sets z to -x and returns z.
func (z *Int) Neg(x *Int) *Int {
z.abs = z.abs.set(x.abs)
diff --git a/src/pkg/big/int_test.go b/src/pkg/big/int_test.go
index 82b5417..66379ca 100755
--- a/src/pkg/big/int_test.go
+++ b/src/pkg/big/int_test.go
@@ -47,6 +47,18 @@
}
+func TestSignZ(t *testing.T) {
+ var zero Int
+ for _, a := range sumZZ {
+ s := a.z.Sign()
+ e := a.z.Cmp(&zero)
+ if s != e {
+ t.Errorf("got %d; want %d for z = %v", s, e, a.z)
+ }
+ }
+}
+
+
func TestSetZ(t *testing.T) {
for _, a := range sumZZ {
var z Int
@@ -61,6 +73,23 @@
}
+func TestAbsZ(t *testing.T) {
+ var zero Int
+ for _, a := range sumZZ {
+ var z Int
+ z.Abs(a.z)
+ var e Int
+ e.Set(a.z)
+ if e.Cmp(&zero) < 0 {
+ e.Sub(&zero, &e)
+ }
+ if z.Cmp(&e) != 0 {
+ t.Errorf("got z = %v; want %v", z, e)
+ }
+ }
+}
+
+
func testFunZZ(t *testing.T, msg string, f funZZ, a argZZ) {
var z Int
f(&z, a.x, a.y)
diff --git a/src/pkg/big/rat.go b/src/pkg/big/rat.go
index c465ab8..d8d6dc4 100644
--- a/src/pkg/big/rat.go
+++ b/src/pkg/big/rat.go
@@ -60,6 +60,23 @@
}
+// Sign returns:
+//
+// -1 if x < 0
+// 0 if x == 0
+// +1 if x > 0
+//
+func (x *Rat) Sign() int {
+ return x.a.Sign()
+}
+
+
+// IsInt returns true if the denominator of x is 1.
+func (x *Rat) IsInt() bool {
+ return len(x.b) == 1 && x.b[0] == 1
+}
+
+
// Num returns the numerator of z; it may be <= 0.
// The result is a reference to z's numerator; it
// may change if a new value is assigned to z.
@@ -126,6 +143,14 @@
}
+// Abs sets z to |x| (the absolute value of x) and returns z.
+func (z *Rat) Abs(x *Rat) *Rat {
+ z.a.Abs(&x.a)
+ z.b = z.b.set(x.b)
+ return z
+}
+
+
// Add sets z to the sum x+y and returns z.
func (z *Rat) Add(x, y *Rat) *Rat {
a1 := mulNat(&x.a, y.b)
diff --git a/src/pkg/big/rat_test.go b/src/pkg/big/rat_test.go
index c74ec85..a3793b2 100644
--- a/src/pkg/big/rat_test.go
+++ b/src/pkg/big/rat_test.go
@@ -84,6 +84,20 @@
}
+func TestRatSign(t *testing.T) {
+ zero := NewRat(0, 1)
+ for _, a := range setStringTests {
+ var x Rat
+ x.SetString(a.in)
+ s := x.Sign()
+ e := x.Cmp(zero)
+ if s != e {
+ t.Errorf("got %d; want %d for z = %v", s, e, &x)
+ }
+ }
+}
+
+
type ratCmpTest struct {
rat1, rat2 string
out int
@@ -114,6 +128,38 @@
}
+func TestIsInt(t *testing.T) {
+ one := NewInt(1)
+ for _, a := range setStringTests {
+ var x Rat
+ x.SetString(a.in)
+ i := x.IsInt()
+ e := x.Denom().Cmp(one) == 0
+ if i != e {
+ t.Errorf("got %v; want %v for z = %v", i, e, &x)
+ }
+ }
+}
+
+
+func TestRatAbs(t *testing.T) {
+ zero := NewRat(0, 1)
+ for _, a := range setStringTests {
+ var z Rat
+ z.SetString(a.in)
+ var e Rat
+ e.Set(&z)
+ if e.Cmp(zero) < 0 {
+ e.Sub(zero, &e)
+ }
+ z.Abs(&z)
+ if z.Cmp(&e) != 0 {
+ t.Errorf("got z = %v; want %v", &z, &e)
+ }
+ }
+}
+
+
type ratBinFun func(z, x, y *Rat) *Rat
type ratBinArg struct {
x, y, z string
