math/big: move "bits" operations used for Float tests into separate file

This is a pure code move without any semantic change.

Change-Id: I2c18efc858955d07949b1241e793232f2cf1deb9
Reviewed-on: https://go-review.googlesource.com/6821Reviewed-by: Alan Donovan <adonovan@google.com>

src/math/big/bits_test.go

+// Copyright 2015 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 big
+
+import (
+	"fmt"
+	"sort"
+	"testing"
+)
+
+func addBits(x, y []int) []int {
+	return append(x, y...)
+}
+
+func mulBits(x, y []int) []int {
+	var p []int
+	for _, x := range x {
+		for _, y := range y {
+			p = append(p, x+y)
+		}
+	}
+	return p
+}
+
+func TestMulBits(t *testing.T) {
+	for _, test := range []struct {
+		x, y, want []int
+	}{
+		{nil, nil, nil},
+		{[]int{}, []int{}, nil},
+		{[]int{0}, []int{0}, []int{0}},
+		{[]int{0}, []int{1}, []int{1}},
+		{[]int{1}, []int{1, 2, 3}, []int{2, 3, 4}},
+		{[]int{-1}, []int{1}, []int{0}},
+		{[]int{-10, -1, 0, 1, 10}, []int{1, 2, 3}, []int{-9, -8, -7, 0, 1, 2, 1, 2, 3, 2, 3, 4, 11, 12, 13}},
+	} {
+		got := fmt.Sprintf("%v", mulBits(test.x, test.y))
+		want := fmt.Sprintf("%v", test.want)
+		if got != want {
+			t.Errorf("%v * %v = %s; want %s", test.x, test.y, got, want)
+		}
+
+	}
+}
+
+// normBits returns the normalized bits for x: It
+// removes multiple equal entries by treating them
+// as an addition (e.g., []int{5, 5} => []int{6}),
+// and it sorts the result list for reproducible
+// results.
+func normBits(x []int) []int {
+	m := make(map[int]bool)
+	for _, b := range x {
+		for m[b] {
+			m[b] = false
+			b++
+		}
+		m[b] = true
+	}
+	var z []int
+	for b, set := range m {
+		if set {
+			z = append(z, b)
+		}
+	}
+	sort.Ints(z)
+	return z
+}
+
+func TestNormBits(t *testing.T) {
+	for _, test := range []struct {
+		x, want []int
+	}{
+		{nil, nil},
+		{[]int{}, []int{}},
+		{[]int{0}, []int{0}},
+		{[]int{0, 0}, []int{1}},
+		{[]int{3, 1, 1}, []int{2, 3}},
+		{[]int{10, 9, 8, 7, 6, 6}, []int{11}},
+	} {
+		got := fmt.Sprintf("%v", normBits(test.x))
+		want := fmt.Sprintf("%v", test.want)
+		if got != want {
+			t.Errorf("normBits(%v) = %s; want %s", test.x, got, want)
+		}
+
+	}
+}
+
+// roundBits returns the Float value rounded to prec bits
+// according to mode from the bit set x.
+func roundBits(x []int, prec uint, mode RoundingMode) *Float {
+	x = normBits(x)
+
+	// determine range
+	var min, max int
+	for i, b := range x {
+		if i == 0 || b < min {
+			min = b
+		}
+		if i == 0 || b > max {
+			max = b
+		}
+	}
+	prec0 := uint(max + 1 - min)
+	if prec >= prec0 {
+		return fromBits(x)
+	}
+	// prec < prec0
+
+	// determine bit 0, rounding, and sticky bit, and result bits z
+	var bit0, rbit, sbit uint
+	var z []int
+	r := max - int(prec)
+	for _, b := range x {
+		switch {
+		case b == r:
+			rbit = 1
+		case b < r:
+			sbit = 1
+		default:
+			// b > r
+			if b == r+1 {
+				bit0 = 1
+			}
+			z = append(z, b)
+		}
+	}
+
+	// round
+	f := fromBits(z) // rounded to zero
+	if mode == ToNearestAway {
+		panic("not yet implemented")
+	}
+	if mode == ToNearestEven && rbit == 1 && (sbit == 1 || sbit == 0 && bit0 != 0) || mode == AwayFromZero {
+		// round away from zero
+		f.SetMode(ToZero).SetPrec(prec)
+		f.Add(f, fromBits([]int{int(r) + 1}))
+	}
+	return f
+}
+
+// fromBits returns the *Float z of the smallest possible precision
+// such that z = sum(2**bits[i]), with i = range bits.
+// If multiple bits[i] are equal, they are added: fromBits(0, 1, 0)
+// == 2**1 + 2**0 + 2**0 = 4.
+func fromBits(bits []int) *Float {
+	// handle 0
+	if len(bits) == 0 {
+		return new(Float)
+	}
+	// len(bits) > 0
+
+	// determine lsb exponent
+	var min int
+	for i, b := range bits {
+		if i == 0 || b < min {
+			min = b
+		}
+	}
+
+	// create bit pattern
+	x := NewInt(0)
+	for _, b := range bits {
+		badj := b - min
+		// propagate carry if necessary
+		for x.Bit(badj) != 0 {
+			x.SetBit(x, badj, 0)
+			badj++
+		}
+		x.SetBit(x, badj, 1)
+	}
+
+	// create corresponding float
+	z := new(Float).SetInt(x) // normalized
+	z.setExp(int64(z.exp) + int64(min))
+	return z
+}
+
+func TestFromBits(t *testing.T) {
+	for _, test := range []struct {
+		bits []int
+		want string
+	}{
+		// all different bit numbers
+		{nil, "0"},
+		{[]int{0}, "0x.8p1"},
+		{[]int{1}, "0x.8p2"},
+		{[]int{-1}, "0x.8p0"},
+		{[]int{63}, "0x.8p64"},
+		{[]int{33, -30}, "0x.8000000000000001p34"},
+		{[]int{255, 0}, "0x.8000000000000000000000000000000000000000000000000000000000000001p256"},
+
+		// multiple equal bit numbers
+		{[]int{0, 0}, "0x.8p2"},
+		{[]int{0, 0, 0, 0}, "0x.8p3"},
+		{[]int{0, 1, 0}, "0x.8p3"},
+		{append([]int{2, 1, 0} /* 7 */, []int{3, 1} /* 10 */ ...), "0x.88p5" /* 17 */},
+	} {
+		f := fromBits(test.bits)
+		if got := f.Format('p', 0); got != test.want {
+			t.Errorf("setBits(%v) = %s; want %s", test.bits, got, test.want)
+		}
+	}
+}

src/math/big/float_test.go

@@ -7,7 +7,6 @@ package big
 import (
 	"fmt"
 	"math"
-	"sort"
 	"strconv"
 	"strings"
 	"testing"
@@ -1448,199 +1447,3 @@ func TestFloatArithmeticRounding(t *testing.T) {
 func TestFloatCmp(t *testing.T) {
 	// TODO(gri) implement this
 }
-
-func addBits(x, y []int) []int {
-	return append(x, y...)
-}
-
-func mulBits(x, y []int) []int {
-	var p []int
-	for _, x := range x {
-		for _, y := range y {
-			p = append(p, x+y)
-		}
-	}
-	return p
-}
-
-func TestMulBits(t *testing.T) {
-	for _, test := range []struct {
-		x, y, want []int
-	}{
-		{nil, nil, nil},
-		{[]int{}, []int{}, nil},
-		{[]int{0}, []int{0}, []int{0}},
-		{[]int{0}, []int{1}, []int{1}},
-		{[]int{1}, []int{1, 2, 3}, []int{2, 3, 4}},
-		{[]int{-1}, []int{1}, []int{0}},
-		{[]int{-10, -1, 0, 1, 10}, []int{1, 2, 3}, []int{-9, -8, -7, 0, 1, 2, 1, 2, 3, 2, 3, 4, 11, 12, 13}},
-	} {
-		got := fmt.Sprintf("%v", mulBits(test.x, test.y))
-		want := fmt.Sprintf("%v", test.want)
-		if got != want {
-			t.Errorf("%v * %v = %s; want %s", test.x, test.y, got, want)
-		}
-
-	}
-}
-
-// normBits returns the normalized bits for x: It
-// removes multiple equal entries by treating them
-// as an addition (e.g., []int{5, 5} => []int{6}),
-// and it sorts the result list for reproducible
-// results.
-func normBits(x []int) []int {
-	m := make(map[int]bool)
-	for _, b := range x {
-		for m[b] {
-			m[b] = false
-			b++
-		}
-		m[b] = true
-	}
-	var z []int
-	for b, set := range m {
-		if set {
-			z = append(z, b)
-		}
-	}
-	sort.Ints(z)
-	return z
-}
-
-func TestNormBits(t *testing.T) {
-	for _, test := range []struct {
-		x, want []int
-	}{
-		{nil, nil},
-		{[]int{}, []int{}},
-		{[]int{0}, []int{0}},
-		{[]int{0, 0}, []int{1}},
-		{[]int{3, 1, 1}, []int{2, 3}},
-		{[]int{10, 9, 8, 7, 6, 6}, []int{11}},
-	} {
-		got := fmt.Sprintf("%v", normBits(test.x))
-		want := fmt.Sprintf("%v", test.want)
-		if got != want {
-			t.Errorf("normBits(%v) = %s; want %s", test.x, got, want)
-		}
-
-	}
-}
-
-// roundBits returns the Float value rounded to prec bits
-// according to mode from the bit set x.
-func roundBits(x []int, prec uint, mode RoundingMode) *Float {
-	x = normBits(x)
-
-	// determine range
-	var min, max int
-	for i, b := range x {
-		if i == 0 || b < min {
-			min = b
-		}
-		if i == 0 || b > max {
-			max = b
-		}
-	}
-	prec0 := uint(max + 1 - min)
-	if prec >= prec0 {
-		return fromBits(x)
-	}
-	// prec < prec0
-
-	// determine bit 0, rounding, and sticky bit, and result bits z
-	var bit0, rbit, sbit uint
-	var z []int
-	r := max - int(prec)
-	for _, b := range x {
-		switch {
-		case b == r:
-			rbit = 1
-		case b < r:
-			sbit = 1
-		default:
-			// b > r
-			if b == r+1 {
-				bit0 = 1
-			}
-			z = append(z, b)
-		}
-	}
-
-	// round
-	f := fromBits(z) // rounded to zero
-	if mode == ToNearestAway {
-		panic("not yet implemented")
-	}
-	if mode == ToNearestEven && rbit == 1 && (sbit == 1 || sbit == 0 && bit0 != 0) || mode == AwayFromZero {
-		// round away from zero
-		f.SetMode(ToZero).SetPrec(prec)
-		f.Add(f, fromBits([]int{int(r) + 1}))
-	}
-	return f
-}
-
-// fromBits returns the *Float z of the smallest possible precision
-// such that z = sum(2**bits[i]), with i = range bits.
-// If multiple bits[i] are equal, they are added: fromBits(0, 1, 0)
-// == 2**1 + 2**0 + 2**0 = 4.
-func fromBits(bits []int) *Float {
-	// handle 0
-	if len(bits) == 0 {
-		return new(Float)
-	}
-	// len(bits) > 0
-
-	// determine lsb exponent
-	var min int
-	for i, b := range bits {
-		if i == 0 || b < min {
-			min = b
-		}
-	}
-
-	// create bit pattern
-	x := NewInt(0)
-	for _, b := range bits {
-		badj := b - min
-		// propagate carry if necessary
-		for x.Bit(badj) != 0 {
-			x.SetBit(x, badj, 0)
-			badj++
-		}
-		x.SetBit(x, badj, 1)
-	}
-
-	// create corresponding float
-	z := new(Float).SetInt(x) // normalized
-	z.setExp(int64(z.exp) + int64(min))
-	return z
-}
-
-func TestFromBits(t *testing.T) {
-	for _, test := range []struct {
-		bits []int
-		want string
-	}{
-		// all different bit numbers
-		{nil, "0"},
-		{[]int{0}, "0x.8p1"},
-		{[]int{1}, "0x.8p2"},
-		{[]int{-1}, "0x.8p0"},
-		{[]int{63}, "0x.8p64"},
-		{[]int{33, -30}, "0x.8000000000000001p34"},
-		{[]int{255, 0}, "0x.8000000000000000000000000000000000000000000000000000000000000001p256"},
-
-		// multiple equal bit numbers
-		{[]int{0, 0}, "0x.8p2"},
-		{[]int{0, 0, 0, 0}, "0x.8p3"},
-		{[]int{0, 1, 0}, "0x.8p3"},
-		{append([]int{2, 1, 0} /* 7 */, []int{3, 1} /* 10 */ ...), "0x.88p5" /* 17 */},
-	} {
-		f := fromBits(test.bits)
-		if got := f.Format('p', 0); got != test.want {
-			t.Errorf("setBits(%v) = %s; want %s", test.bits, got, test.want)
-		}
-	}
-}