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path: root/src/pkg/strconv/decimal.go
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-rw-r--r--src/pkg/strconv/decimal.go378
1 files changed, 0 insertions, 378 deletions
diff --git a/src/pkg/strconv/decimal.go b/src/pkg/strconv/decimal.go
deleted file mode 100644
index 42601283d..000000000
--- a/src/pkg/strconv/decimal.go
+++ /dev/null
@@ -1,378 +0,0 @@
-// 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.
-
-// Multiprecision decimal numbers.
-// For floating-point formatting only; not general purpose.
-// Only operations are assign and (binary) left/right shift.
-// Can do binary floating point in multiprecision decimal precisely
-// because 2 divides 10; cannot do decimal floating point
-// in multiprecision binary precisely.
-
-package strconv
-
-type decimal struct {
- d [800]byte // digits
- nd int // number of digits used
- dp int // decimal point
- neg bool
- trunc bool // discarded nonzero digits beyond d[:nd]
-}
-
-func (a *decimal) String() string {
- n := 10 + a.nd
- if a.dp > 0 {
- n += a.dp
- }
- if a.dp < 0 {
- n += -a.dp
- }
-
- buf := make([]byte, n)
- w := 0
- switch {
- case a.nd == 0:
- return "0"
-
- case a.dp <= 0:
- // zeros fill space between decimal point and digits
- buf[w] = '0'
- w++
- buf[w] = '.'
- w++
- w += digitZero(buf[w : w+-a.dp])
- w += copy(buf[w:], a.d[0:a.nd])
-
- case a.dp < a.nd:
- // decimal point in middle of digits
- w += copy(buf[w:], a.d[0:a.dp])
- buf[w] = '.'
- w++
- w += copy(buf[w:], a.d[a.dp:a.nd])
-
- default:
- // zeros fill space between digits and decimal point
- w += copy(buf[w:], a.d[0:a.nd])
- w += digitZero(buf[w : w+a.dp-a.nd])
- }
- return string(buf[0:w])
-}
-
-func digitZero(dst []byte) int {
- for i := range dst {
- dst[i] = '0'
- }
- return len(dst)
-}
-
-// trim trailing zeros from number.
-// (They are meaningless; the decimal point is tracked
-// independent of the number of digits.)
-func trim(a *decimal) {
- for a.nd > 0 && a.d[a.nd-1] == '0' {
- a.nd--
- }
- if a.nd == 0 {
- a.dp = 0
- }
-}
-
-// Assign v to a.
-func (a *decimal) Assign(v uint64) {
- var buf [24]byte
-
- // Write reversed decimal in buf.
- n := 0
- for v > 0 {
- v1 := v / 10
- v -= 10 * v1
- buf[n] = byte(v + '0')
- n++
- v = v1
- }
-
- // Reverse again to produce forward decimal in a.d.
- a.nd = 0
- for n--; n >= 0; n-- {
- a.d[a.nd] = buf[n]
- a.nd++
- }
- a.dp = a.nd
- trim(a)
-}
-
-// Maximum shift that we can do in one pass without overflow.
-// Signed int has 31 bits, and we have to be able to accommodate 9<<k.
-const maxShift = 27
-
-// Binary shift right (* 2) by k bits. k <= maxShift to avoid overflow.
-func rightShift(a *decimal, k uint) {
- r := 0 // read pointer
- w := 0 // write pointer
-
- // Pick up enough leading digits to cover first shift.
- n := 0
- for ; n>>k == 0; r++ {
- if r >= a.nd {
- if n == 0 {
- // a == 0; shouldn't get here, but handle anyway.
- a.nd = 0
- return
- }
- for n>>k == 0 {
- n = n * 10
- r++
- }
- break
- }
- c := int(a.d[r])
- n = n*10 + c - '0'
- }
- a.dp -= r - 1
-
- // Pick up a digit, put down a digit.
- for ; r < a.nd; r++ {
- c := int(a.d[r])
- dig := n >> k
- n -= dig << k
- a.d[w] = byte(dig + '0')
- w++
- n = n*10 + c - '0'
- }
-
- // Put down extra digits.
- for n > 0 {
- dig := n >> k
- n -= dig << k
- if w < len(a.d) {
- a.d[w] = byte(dig + '0')
- w++
- } else if dig > 0 {
- a.trunc = true
- }
- n = n * 10
- }
-
- a.nd = w
- trim(a)
-}
-
-// Cheat sheet for left shift: table indexed by shift count giving
-// number of new digits that will be introduced by that shift.
-//
-// For example, leftcheats[4] = {2, "625"}. That means that
-// if we are shifting by 4 (multiplying by 16), it will add 2 digits
-// when the string prefix is "625" through "999", and one fewer digit
-// if the string prefix is "000" through "624".
-//
-// Credit for this trick goes to Ken.
-
-type leftCheat struct {
- delta int // number of new digits
- cutoff string // minus one digit if original < a.
-}
-
-var leftcheats = []leftCheat{
- // Leading digits of 1/2^i = 5^i.
- // 5^23 is not an exact 64-bit floating point number,
- // so have to use bc for the math.
- /*
- seq 27 | sed 's/^/5^/' | bc |
- awk 'BEGIN{ print "\tleftCheat{ 0, \"\" }," }
- {
- log2 = log(2)/log(10)
- printf("\tleftCheat{ %d, \"%s\" },\t// * %d\n",
- int(log2*NR+1), $0, 2**NR)
- }'
- */
- {0, ""},
- {1, "5"}, // * 2
- {1, "25"}, // * 4
- {1, "125"}, // * 8
- {2, "625"}, // * 16
- {2, "3125"}, // * 32
- {2, "15625"}, // * 64
- {3, "78125"}, // * 128
- {3, "390625"}, // * 256
- {3, "1953125"}, // * 512
- {4, "9765625"}, // * 1024
- {4, "48828125"}, // * 2048
- {4, "244140625"}, // * 4096
- {4, "1220703125"}, // * 8192
- {5, "6103515625"}, // * 16384
- {5, "30517578125"}, // * 32768
- {5, "152587890625"}, // * 65536
- {6, "762939453125"}, // * 131072
- {6, "3814697265625"}, // * 262144
- {6, "19073486328125"}, // * 524288
- {7, "95367431640625"}, // * 1048576
- {7, "476837158203125"}, // * 2097152
- {7, "2384185791015625"}, // * 4194304
- {7, "11920928955078125"}, // * 8388608
- {8, "59604644775390625"}, // * 16777216
- {8, "298023223876953125"}, // * 33554432
- {8, "1490116119384765625"}, // * 67108864
- {9, "7450580596923828125"}, // * 134217728
-}
-
-// Is the leading prefix of b lexicographically less than s?
-func prefixIsLessThan(b []byte, s string) bool {
- for i := 0; i < len(s); i++ {
- if i >= len(b) {
- return true
- }
- if b[i] != s[i] {
- return b[i] < s[i]
- }
- }
- return false
-}
-
-// Binary shift left (/ 2) by k bits. k <= maxShift to avoid overflow.
-func leftShift(a *decimal, k uint) {
- delta := leftcheats[k].delta
- if prefixIsLessThan(a.d[0:a.nd], leftcheats[k].cutoff) {
- delta--
- }
-
- r := a.nd // read index
- w := a.nd + delta // write index
- n := 0
-
- // Pick up a digit, put down a digit.
- for r--; r >= 0; r-- {
- n += (int(a.d[r]) - '0') << k
- quo := n / 10
- rem := n - 10*quo
- w--
- if w < len(a.d) {
- a.d[w] = byte(rem + '0')
- } else if rem != 0 {
- a.trunc = true
- }
- n = quo
- }
-
- // Put down extra digits.
- for n > 0 {
- quo := n / 10
- rem := n - 10*quo
- w--
- if w < len(a.d) {
- a.d[w] = byte(rem + '0')
- } else if rem != 0 {
- a.trunc = true
- }
- n = quo
- }
-
- a.nd += delta
- if a.nd >= len(a.d) {
- a.nd = len(a.d)
- }
- a.dp += delta
- trim(a)
-}
-
-// Binary shift left (k > 0) or right (k < 0).
-func (a *decimal) Shift(k int) {
- switch {
- case a.nd == 0:
- // nothing to do: a == 0
- case k > 0:
- for k > maxShift {
- leftShift(a, maxShift)
- k -= maxShift
- }
- leftShift(a, uint(k))
- case k < 0:
- for k < -maxShift {
- rightShift(a, maxShift)
- k += maxShift
- }
- rightShift(a, uint(-k))
- }
-}
-
-// If we chop a at nd digits, should we round up?
-func shouldRoundUp(a *decimal, nd int) bool {
- if nd < 0 || nd >= a.nd {
- return false
- }
- if a.d[nd] == '5' && nd+1 == a.nd { // exactly halfway - round to even
- // if we truncated, a little higher than what's recorded - always round up
- if a.trunc {
- return true
- }
- return nd > 0 && (a.d[nd-1]-'0')%2 != 0
- }
- // not halfway - digit tells all
- return a.d[nd] >= '5'
-}
-
-// Round a to nd digits (or fewer).
-// If nd is zero, it means we're rounding
-// just to the left of the digits, as in
-// 0.09 -> 0.1.
-func (a *decimal) Round(nd int) {
- if nd < 0 || nd >= a.nd {
- return
- }
- if shouldRoundUp(a, nd) {
- a.RoundUp(nd)
- } else {
- a.RoundDown(nd)
- }
-}
-
-// Round a down to nd digits (or fewer).
-func (a *decimal) RoundDown(nd int) {
- if nd < 0 || nd >= a.nd {
- return
- }
- a.nd = nd
- trim(a)
-}
-
-// Round a up to nd digits (or fewer).
-func (a *decimal) RoundUp(nd int) {
- if nd < 0 || nd >= a.nd {
- return
- }
-
- // round up
- for i := nd - 1; i >= 0; i-- {
- c := a.d[i]
- if c < '9' { // can stop after this digit
- a.d[i]++
- a.nd = i + 1
- return
- }
- }
-
- // Number is all 9s.
- // Change to single 1 with adjusted decimal point.
- a.d[0] = '1'
- a.nd = 1
- a.dp++
-}
-
-// Extract integer part, rounded appropriately.
-// No guarantees about overflow.
-func (a *decimal) RoundedInteger() uint64 {
- if a.dp > 20 {
- return 0xFFFFFFFFFFFFFFFF
- }
- var i int
- n := uint64(0)
- for i = 0; i < a.dp && i < a.nd; i++ {
- n = n*10 + uint64(a.d[i]-'0')
- }
- for ; i < a.dp; i++ {
- n *= 10
- }
- if shouldRoundUp(a, a.dp) {
- n++
- }
- return n
-}
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