Mercurial > repos > gianmarco_piccinno > cs_tool_project_rm

comparison cachingseq.py @ 0:5397da1ef896 draft

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author gianmarco_piccinno
date Tue, 21 May 2019 05:05:15 -0400
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-1:000000000000 0:5397da1ef896
1 #!/usr/bin/env python2
2 #
3 # Copyright 2011-2016 Google Inc.
4 #
5 # Licensed under the Apache License, Version 2.0 (the "License");
6 # you may not use this file except in compliance with the License.
7 # You may obtain a copy of the License at
8 #
9 # http://www.apache.org/licenses/LICENSE-2.0
10 #
11 # Unless required by applicable law or agreed to in writing, software
12 # distributed under the License is distributed on an "AS IS" BASIS,
13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 # See the License for the specific language governing permissions and
15 # limitations under the License.
16 #
17 # vim: sw=2 sts=2 et
18
19 class CachingFuncSequence(object):
20 def __init__(self, func, length, inc_func=None):
21 """
22 length: Length of this sequence.
23 func: function(index)
24 inc_func: function(index, value_of_previous)
25 """
26
27 self.func = func
28 self.inc_func = inc_func
29 self.length = length
30 self._cache = {}
31
32 def __getitem__(self, i):
33 if i < 0:
34 i += self.length
35 if i < 0 or i >= self.length:
36 raise IndexError()
37
38 v = self._cache.get(i)
39 if v is not None:
40 return v
41
42 if self.inc_func and i-1 in self._cache:
43 v = self.inc_func(i, self._cache[i-1])
44 else:
45 v = self.func(i)
46
47 self._cache[i] = v
48 return v
49
50 def __len__(self):
51 return self.length
52
53 def __iter__(self):
54 for i in range(self.length):
55 yield self[i]