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1 // Copyright 2009 The Go Authors. All rights reserved.
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2 // Use of this source code is governed by a BSD-style
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3 // license that can be found in the LICENSE file.
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4
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5 // +build ignore
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6
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7 package main
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8
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9 import (
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10 big "."
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11 "fmt"
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12 "runtime"
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13 )
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14
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15 var (
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16 tmp1 = big.NewInt(0)
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17 tmp2 = big.NewInt(0)
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18 numer = big.NewInt(1)
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19 accum = big.NewInt(0)
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20 denom = big.NewInt(1)
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21 ten = big.NewInt(10)
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22 )
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23
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24 func extractDigit() int64 {
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25 if big.CmpInt(numer, accum) > 0 {
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26 return -1
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27 }
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28 tmp1.Lsh(numer, 1).Add(tmp1, numer).Add(tmp1, accum)
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29 big.DivModInt(tmp1, tmp2, tmp1, denom)
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30 tmp2.Add(tmp2, numer)
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31 if big.CmpInt(tmp2, denom) >= 0 {
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32 return -1
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33 }
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34 return tmp1.Int64()
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35 }
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36
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37 func nextTerm(k int64) {
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38 y2 := k*2 + 1
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39 accum.Add(accum, tmp1.Lsh(numer, 1))
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40 accum.Mul(accum, tmp1.SetInt64(y2))
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41 numer.Mul(numer, tmp1.SetInt64(k))
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42 denom.Mul(denom, tmp1.SetInt64(y2))
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43 }
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44
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45 func eliminateDigit(d int64) {
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46 accum.Sub(accum, tmp1.Mul(denom, tmp1.SetInt64(d)))
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47 accum.Mul(accum, ten)
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48 numer.Mul(numer, ten)
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49 }
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50
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51 func main() {
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52 i := 0
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53 k := int64(0)
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54 for {
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55 d := int64(-1)
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56 for d < 0 {
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57 k++
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58 nextTerm(k)
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59 d = extractDigit()
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60 }
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61 eliminateDigit(d)
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62 fmt.Printf("%c", d+'0')
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63
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64 if i++; i%50 == 0 {
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65 fmt.Printf("\n")
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66 if i >= 1000 {
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67 break
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68 }
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69 }
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70 }
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71
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72 fmt.Printf("\n%d calls; bit sizes: %d %d %d\n", runtime.NumCgoCall(), numer.Len(), accum.Len(), denom.Len())
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73 }
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