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1 ##############################################################################
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2 #
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3 # Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
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4 #
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5 # This software is subject to the provisions of the Zope Public License,
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6 # Version 2.0 (ZPL). A copy of the ZPL should accompany this distribution.
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7 # THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
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8 # WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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9 # WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
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10 # FOR A PARTICULAR PURPOSE
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11 #
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12 ##############################################################################
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13 __doc__='''Iterator class
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14
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15 Unlike the builtin iterators of Python 2.2+, these classes are
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16 designed to maintain information about the state of an iteration.
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17 The Iterator() function accepts either a sequence or a Python
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18 iterator. The next() method fetches the next item, and returns
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19 true if it succeeds.
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20
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21 $Id: Iterator.py,v 1.2 2002-09-26 21:54:17 richard Exp $'''
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22 __version__='$Revision: 1.2 $'[11:-2]
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23
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24 import string
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25
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26 class Iterator:
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27 '''Simple Iterator class'''
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28
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29 __allow_access_to_unprotected_subobjects__ = 1
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30
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31 nextIndex = 0
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32 def __init__(self, seq):
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33 self.seq = seq
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34 for inner in seqInner, iterInner:
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35 if inner._supports(seq):
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36 self._inner = inner
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37 self._prep_next = inner.prep_next
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38 return
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39 raise TypeError, "Iterator does not support %s" % `seq`
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40
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41 def __getattr__(self, name):
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42 try:
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43 inner = getattr(self._inner, 'it_' + name)
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44 except AttributeError:
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45 raise AttributeError, name
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46 return inner(self)
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47
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48 def next(self):
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49 if not (hasattr(self, '_next') or self._prep_next(self)):
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50 return 0
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51 self.index = i = self.nextIndex
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52 self.nextIndex = i+1
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53 self._advance(self)
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54 return 1
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55
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56 def _advance(self, it):
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57 self.item = self._next
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58 del self._next
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59 del self.end
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60 self._advance = self._inner.advance
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61 self.start = 1
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62
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63 def number(self): return self.nextIndex
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64
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65 def even(self): return not self.index % 2
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66
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67 def odd(self): return self.index % 2
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68
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69 def letter(self, base=ord('a'), radix=26):
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70 index = self.index
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71 s = ''
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72 while 1:
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73 index, off = divmod(index, radix)
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74 s = chr(base + off) + s
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75 if not index: return s
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76
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77 def Letter(self):
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78 return self.letter(base=ord('A'))
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79
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80 def Roman(self, rnvalues=(
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81 (1000,'M'),(900,'CM'),(500,'D'),(400,'CD'),
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82 (100,'C'),(90,'XC'),(50,'L'),(40,'XL'),
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83 (10,'X'),(9,'IX'),(5,'V'),(4,'IV'),(1,'I')) ):
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84 n = self.index + 1
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85 s = ''
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86 for v, r in rnvalues:
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87 rct, n = divmod(n, v)
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88 s = s + r * rct
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89 return s
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90
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91 def roman(self, lower=string.lower):
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92 return lower(self.Roman())
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93
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94 def first(self, name=None):
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95 if self.start: return 1
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96 return not self.same_part(name, self._last, self.item)
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97
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98 def last(self, name=None):
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99 if self.end: return 1
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100 return not self.same_part(name, self.item, self._next)
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101
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102 def same_part(self, name, ob1, ob2):
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103 if name is None:
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104 return ob1 == ob2
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105 no = []
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106 return getattr(ob1, name, no) == getattr(ob2, name, no) is not no
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107
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108 def __iter__(self):
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109 return IterIter(self)
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110
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111 class InnerBase:
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112 '''Base Inner class for Iterators'''
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113 # Prep sets up ._next and .end
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114 def prep_next(self, it):
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115 it.next = self.no_next
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116 it.end = 1
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117 return 0
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118
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119 # Advance knocks them down
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120 def advance(self, it):
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121 it._last = it.item
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122 it.item = it._next
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123 del it._next
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124 del it.end
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125 it.start = 0
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126
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127 def no_next(self, it):
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128 return 0
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129
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130 def it_end(self, it):
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131 if hasattr(it, '_next'):
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132 return 0
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133 return not self.prep_next(it)
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134
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135 class SeqInner(InnerBase):
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136 '''Inner class for sequence Iterators'''
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137
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138 def _supports(self, ob):
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139 try: ob[0]
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140 except (TypeError, AttributeError): return 0
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141 except: pass
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142 return 1
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143
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144 def prep_next(self, it):
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145 i = it.nextIndex
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146 try:
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147 it._next = it.seq[i]
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148 except IndexError:
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149 it._prep_next = self.no_next
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150 it.end = 1
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151 return 0
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152 it.end = 0
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153 return 1
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154
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155 def it_length(self, it):
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156 it.length = l = len(it.seq)
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157 return l
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158
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159 try:
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160 StopIteration=StopIteration
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161 except NameError:
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162 StopIteration="StopIteration"
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163
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164 class IterInner(InnerBase):
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165 '''Iterator inner class for Python iterators'''
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166
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167 def _supports(self, ob):
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168 try:
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169 if hasattr(ob, 'next') and (ob is iter(ob)):
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170 return 1
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171 except:
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172 return 0
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173
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174 def prep_next(self, it):
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175 try:
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176 it._next = it.seq.next()
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177 except StopIteration:
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178 it._prep_next = self.no_next
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179 it.end = 1
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180 return 0
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181 it.end = 0
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182 return 1
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183
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184 class IterIter:
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185 def __init__(self, it):
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186 self.it = it
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187 self.skip = it.nextIndex > 0 and not it.end
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188 def next(self):
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189 it = self.it
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190 if self.skip:
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191 self.skip = 0
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192 return it.item
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193 if it.next():
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194 return it.item
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195 raise StopIteration
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196
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197 seqInner = SeqInner()
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198 iterInner = IterInner()
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