math/big: replace nat{} -> nat(nil)
No need for creating a new nat each time.
Per Roger Peppe's suggestion; assuming
nat(nil) produces better code than nat{}.
R=rsc
CC=golang-dev
https://golang.org/cl/5375092
diff --git a/src/pkg/math/big/int.go b/src/pkg/math/big/int.go
index 2558be5..35e2e29 100644
--- a/src/pkg/math/big/int.go
+++ b/src/pkg/math/big/int.go
@@ -176,7 +176,7 @@
// If y == 0, a division-by-zero run-time panic occurs.
// Rem implements truncated modulus (like Go); see QuoRem for more details.
func (z *Int) Rem(x, y *Int) *Int {
- _, z.abs = nat{}.div(z.abs, x.abs, y.abs)
+ _, z.abs = nat(nil).div(z.abs, x.abs, y.abs)
z.neg = len(z.abs) > 0 && x.neg // 0 has no sign
return z
}
@@ -678,7 +678,7 @@
panic("negative bit index")
}
if z.neg {
- t := nat{}.sub(z.abs, natOne)
+ t := nat(nil).sub(z.abs, natOne)
return t.bit(uint(i)) ^ 1
}
@@ -710,8 +710,8 @@
if x.neg == y.neg {
if x.neg {
// (-x) & (-y) == ^(x-1) & ^(y-1) == ^((x-1) | (y-1)) == -(((x-1) | (y-1)) + 1)
- x1 := nat{}.sub(x.abs, natOne)
- y1 := nat{}.sub(y.abs, natOne)
+ x1 := nat(nil).sub(x.abs, natOne)
+ y1 := nat(nil).sub(y.abs, natOne)
z.abs = z.abs.add(z.abs.or(x1, y1), natOne)
z.neg = true // z cannot be zero if x and y are negative
return z
@@ -729,7 +729,7 @@
}
// x & (-y) == x & ^(y-1) == x &^ (y-1)
- y1 := nat{}.sub(y.abs, natOne)
+ y1 := nat(nil).sub(y.abs, natOne)
z.abs = z.abs.andNot(x.abs, y1)
z.neg = false
return z
@@ -740,8 +740,8 @@
if x.neg == y.neg {
if x.neg {
// (-x) &^ (-y) == ^(x-1) &^ ^(y-1) == ^(x-1) & (y-1) == (y-1) &^ (x-1)
- x1 := nat{}.sub(x.abs, natOne)
- y1 := nat{}.sub(y.abs, natOne)
+ x1 := nat(nil).sub(x.abs, natOne)
+ y1 := nat(nil).sub(y.abs, natOne)
z.abs = z.abs.andNot(y1, x1)
z.neg = false
return z
@@ -755,14 +755,14 @@
if x.neg {
// (-x) &^ y == ^(x-1) &^ y == ^(x-1) & ^y == ^((x-1) | y) == -(((x-1) | y) + 1)
- x1 := nat{}.sub(x.abs, natOne)
+ x1 := nat(nil).sub(x.abs, natOne)
z.abs = z.abs.add(z.abs.or(x1, y.abs), natOne)
z.neg = true // z cannot be zero if x is negative and y is positive
return z
}
// x &^ (-y) == x &^ ^(y-1) == x & (y-1)
- y1 := nat{}.add(y.abs, natOne)
+ y1 := nat(nil).add(y.abs, natOne)
z.abs = z.abs.and(x.abs, y1)
z.neg = false
return z
@@ -773,8 +773,8 @@
if x.neg == y.neg {
if x.neg {
// (-x) | (-y) == ^(x-1) | ^(y-1) == ^((x-1) & (y-1)) == -(((x-1) & (y-1)) + 1)
- x1 := nat{}.sub(x.abs, natOne)
- y1 := nat{}.sub(y.abs, natOne)
+ x1 := nat(nil).sub(x.abs, natOne)
+ y1 := nat(nil).sub(y.abs, natOne)
z.abs = z.abs.add(z.abs.and(x1, y1), natOne)
z.neg = true // z cannot be zero if x and y are negative
return z
@@ -792,7 +792,7 @@
}
// x | (-y) == x | ^(y-1) == ^((y-1) &^ x) == -(^((y-1) &^ x) + 1)
- y1 := nat{}.sub(y.abs, natOne)
+ y1 := nat(nil).sub(y.abs, natOne)
z.abs = z.abs.add(z.abs.andNot(y1, x.abs), natOne)
z.neg = true // z cannot be zero if one of x or y is negative
return z
@@ -803,8 +803,8 @@
if x.neg == y.neg {
if x.neg {
// (-x) ^ (-y) == ^(x-1) ^ ^(y-1) == (x-1) ^ (y-1)
- x1 := nat{}.sub(x.abs, natOne)
- y1 := nat{}.sub(y.abs, natOne)
+ x1 := nat(nil).sub(x.abs, natOne)
+ y1 := nat(nil).sub(y.abs, natOne)
z.abs = z.abs.xor(x1, y1)
z.neg = false
return z
@@ -822,7 +822,7 @@
}
// x ^ (-y) == x ^ ^(y-1) == ^(x ^ (y-1)) == -((x ^ (y-1)) + 1)
- y1 := nat{}.sub(y.abs, natOne)
+ y1 := nat(nil).sub(y.abs, natOne)
z.abs = z.abs.add(z.abs.xor(x.abs, y1), natOne)
z.neg = true // z cannot be zero if only one of x or y is negative
return z
diff --git a/src/pkg/math/big/nat.go b/src/pkg/math/big/nat.go
index 3fa41e7..eee8ee3 100644
--- a/src/pkg/math/big/nat.go
+++ b/src/pkg/math/big/nat.go
@@ -447,10 +447,10 @@
case a == b:
return z.setUint64(a)
case a+1 == b:
- return z.mul(nat{}.setUint64(a), nat{}.setUint64(b))
+ return z.mul(nat(nil).setUint64(a), nat(nil).setUint64(b))
}
m := (a + b) / 2
- return z.mul(nat{}.mulRange(a, m), nat{}.mulRange(m+1, b))
+ return z.mul(nat(nil).mulRange(a, m), nat(nil).mulRange(m+1, b))
}
// q = (x-r)/y, with 0 <= r < y
@@ -785,7 +785,7 @@
}
// preserve x, create local copy for use in repeated divisions
- q := nat{}.set(x)
+ q := nat(nil).set(x)
var r Word
// convert
@@ -1191,11 +1191,11 @@
return false
}
- nm1 := nat{}.sub(n, natOne)
+ nm1 := nat(nil).sub(n, natOne)
// 1<<k * q = nm1;
q, k := nm1.powersOfTwoDecompose()
- nm3 := nat{}.sub(nm1, natTwo)
+ nm3 := nat(nil).sub(nm1, natTwo)
rand := rand.New(rand.NewSource(int64(n[0])))
var x, y, quotient nat
diff --git a/src/pkg/math/big/nat_test.go b/src/pkg/math/big/nat_test.go
index 041a6c4..b208646 100644
--- a/src/pkg/math/big/nat_test.go
+++ b/src/pkg/math/big/nat_test.go
@@ -16,9 +16,9 @@
r int
}{
{nil, nil, 0},
- {nil, nat{}, 0},
- {nat{}, nil, 0},
- {nat{}, nat{}, 0},
+ {nil, nat(nil), 0},
+ {nat(nil), nil, 0},
+ {nat(nil), nat(nil), 0},
{nat{0}, nat{0}, 0},
{nat{0}, nat{1}, -1},
{nat{1}, nat{0}, 1},
@@ -67,7 +67,7 @@
func TestSet(t *testing.T) {
for _, a := range sumNN {
- z := nat{}.set(a.z)
+ z := nat(nil).set(a.z)
if z.cmp(a.z) != 0 {
t.Errorf("got z = %v; want %v", z, a.z)
}
@@ -129,7 +129,7 @@
func TestMulRangeN(t *testing.T) {
for i, r := range mulRangesN {
- prod := nat{}.mulRange(r.a, r.b).decimalString()
+ prod := nat(nil).mulRange(r.a, r.b).decimalString()
if prod != r.prod {
t.Errorf("#%d: got %s; want %s", i, prod, r.prod)
}
@@ -175,7 +175,7 @@
s := make([]byte, i)
// don't destroy x
- q := nat{}.set(x)
+ q := nat(nil).set(x)
// convert
for len(q) > 0 {
@@ -212,7 +212,7 @@
t.Errorf("string%+v\n\tgot s = %s; want %s", a, s, a.s)
}
- x, b, err := nat{}.scan(strings.NewReader(a.s), len(a.c))
+ x, b, err := nat(nil).scan(strings.NewReader(a.s), len(a.c))
if x.cmp(a.x) != 0 {
t.Errorf("scan%+v\n\tgot z = %v; want %v", a, x, a.x)
}
@@ -271,7 +271,7 @@
func TestScanBase(t *testing.T) {
for _, a := range natScanTests {
r := strings.NewReader(a.s)
- x, b, err := nat{}.scan(r, a.base)
+ x, b, err := nat(nil).scan(r, a.base)
if err == nil && !a.ok {
t.Errorf("scan%+v\n\texpected error", a)
}
@@ -651,17 +651,17 @@
func TestExpNN(t *testing.T) {
for i, test := range expNNTests {
- x, _, _ := nat{}.scan(strings.NewReader(test.x), 0)
- y, _, _ := nat{}.scan(strings.NewReader(test.y), 0)
- out, _, _ := nat{}.scan(strings.NewReader(test.out), 0)
+ x, _, _ := nat(nil).scan(strings.NewReader(test.x), 0)
+ y, _, _ := nat(nil).scan(strings.NewReader(test.y), 0)
+ out, _, _ := nat(nil).scan(strings.NewReader(test.out), 0)
var m nat
if len(test.m) > 0 {
- m, _, _ = nat{}.scan(strings.NewReader(test.m), 0)
+ m, _, _ = nat(nil).scan(strings.NewReader(test.m), 0)
}
- z := nat{}.expNN(x, y, m)
+ z := nat(nil).expNN(x, y, m)
if z.cmp(out) != 0 {
t.Errorf("#%d got %v want %v", i, z, out)
}
diff --git a/src/pkg/math/big/rat.go b/src/pkg/math/big/rat.go
index 3a0add3..adf4124 100644
--- a/src/pkg/math/big/rat.go
+++ b/src/pkg/math/big/rat.go
@@ -33,7 +33,7 @@
panic("division by zero")
}
if &z.a == b || alias(z.a.abs, babs) {
- babs = nat{}.set(babs) // make a copy
+ babs = nat(nil).set(babs) // make a copy
}
z.a.abs = z.a.abs.set(a.abs)
z.b = z.b.set(babs)
@@ -315,7 +315,7 @@
if _, ok := z.a.SetString(s, 10); !ok {
return nil, false
}
- powTen := nat{}.expNN(natTen, exp.abs, nil)
+ powTen := nat(nil).expNN(natTen, exp.abs, nil)
if exp.neg {
z.b = powTen
z.norm()
@@ -357,23 +357,23 @@
}
// z.b != 0
- q, r := nat{}.div(nat{}, z.a.abs, z.b)
+ q, r := nat(nil).div(nat(nil), z.a.abs, z.b)
p := natOne
if prec > 0 {
- p = nat{}.expNN(natTen, nat{}.setUint64(uint64(prec)), nil)
+ p = nat(nil).expNN(natTen, nat(nil).setUint64(uint64(prec)), nil)
}
r = r.mul(r, p)
- r, r2 := r.div(nat{}, r, z.b)
+ r, r2 := r.div(nat(nil), r, z.b)
// see if we need to round up
r2 = r2.add(r2, r2)
if z.b.cmp(r2) <= 0 {
r = r.add(r, natOne)
if r.cmp(p) >= 0 {
- q = nat{}.add(q, natOne)
- r = nat{}.sub(r, p)
+ q = nat(nil).add(q, natOne)
+ r = nat(nil).sub(r, p)
}
}
