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# -*- test-case-name: epsilon.test.test_view -*-
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Utility functionality for creating wrapping sequences so as to transform
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their indices in some manner.
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class SlicedView(object):
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Wrapper around a sequence which allows indexing and non-extended
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slicing, adjusting all indices using a transformation defined by a
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t = SlicedView(s, slice(1, None))
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@ivar sequence: The underlying sequence from which to retrieve elements.
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@ivar bounds: A C{slice} instance defining the boundaries of this view.
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def __init__(self, sequence, bounds):
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self.sequence = sequence
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def _getIndices(self):
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start, stop, step = self.bounds.indices(len(self.sequence))
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indices = xrange(start, stop, step)
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def __getitem__(self, index):
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Compute the index in the underlying sequence of the given view index
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and return the corresponding element.
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@raise IndexError: If C{index} is out of bounds for the view.
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@raise ValueError: If C{self.bounds} is out of bounds for
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if isinstance(index, slice):
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return SlicedView(self, index)
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return self.sequence[self._getIndices()[index]]
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Compute the length of this view onto the sequence and return it.
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return len(self._getIndices())
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Epsilon/epsilon/view.py
