279 lines
10 KiB
Python
279 lines
10 KiB
Python
# This file is part of Hypothesis, which may be found at
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# https://github.com/HypothesisWorks/hypothesis/
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#
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# Copyright the Hypothesis Authors.
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# Individual contributors are listed in AUTHORS.rst and the git log.
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#
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# This Source Code Form is subject to the terms of the Mozilla Public License,
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# v. 2.0. If a copy of the MPL was not distributed with this file, You can
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# obtain one at https://mozilla.org/MPL/2.0/.
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from typing import Union
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class IntervalSet:
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@classmethod
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def from_string(cls, s):
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"""Return a tuple of intervals, covering the codepoints of characters in `s`.
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>>> IntervalSet.from_string('abcdef0123456789')
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((48, 57), (97, 102))
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"""
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x = cls((ord(c), ord(c)) for c in sorted(s))
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return x.union(x)
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def __init__(self, intervals):
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self.intervals = tuple(intervals)
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self.offsets = [0]
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for u, v in self.intervals:
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self.offsets.append(self.offsets[-1] + v - u + 1)
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self.size = self.offsets.pop()
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self._idx_of_zero = self.index_above(ord("0"))
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self._idx_of_Z = min(self.index_above(ord("Z")), len(self) - 1)
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def __len__(self):
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return self.size
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def __iter__(self):
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for u, v in self.intervals:
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yield from range(u, v + 1)
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def __getitem__(self, i):
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if i < 0:
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i = self.size + i
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if i < 0 or i >= self.size:
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raise IndexError(f"Invalid index {i} for [0, {self.size})")
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# Want j = maximal such that offsets[j] <= i
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j = len(self.intervals) - 1
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if self.offsets[j] > i:
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hi = j
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lo = 0
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# Invariant: offsets[lo] <= i < offsets[hi]
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while lo + 1 < hi:
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mid = (lo + hi) // 2
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if self.offsets[mid] <= i:
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lo = mid
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else:
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hi = mid
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j = lo
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t = i - self.offsets[j]
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u, v = self.intervals[j]
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r = u + t
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assert r <= v
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return r
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def __contains__(self, elem: Union[str, int]) -> bool:
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if isinstance(elem, str):
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elem = ord(elem)
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assert 0 <= elem <= 0x10FFFF
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return any(start <= elem <= end for start, end in self.intervals)
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def __repr__(self):
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return f"IntervalSet({self.intervals!r})"
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def index(self, value: int) -> int:
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for offset, (u, v) in zip(self.offsets, self.intervals):
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if u == value:
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return offset
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elif u > value:
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raise ValueError(f"{value} is not in list")
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if value <= v:
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return offset + (value - u)
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raise ValueError(f"{value} is not in list")
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def index_above(self, value: int) -> int:
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for offset, (u, v) in zip(self.offsets, self.intervals):
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if u >= value:
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return offset
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if value <= v:
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return offset + (value - u)
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return self.size
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def __or__(self, other):
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return self.union(other)
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def __sub__(self, other):
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return self.difference(other)
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def __and__(self, other):
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return self.intersection(other)
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def union(self, other):
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"""Merge two sequences of intervals into a single tuple of intervals.
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Any integer bounded by `x` or `y` is also bounded by the result.
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>>> union([(3, 10)], [(1, 2), (5, 17)])
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((1, 17),)
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"""
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assert isinstance(other, type(self))
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x = self.intervals
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y = other.intervals
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if not x:
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return IntervalSet((u, v) for u, v in y)
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if not y:
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return IntervalSet((u, v) for u, v in x)
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intervals = sorted(x + y, reverse=True)
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result = [intervals.pop()]
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while intervals:
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# 1. intervals is in descending order
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# 2. pop() takes from the RHS.
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# 3. (a, b) was popped 1st, then (u, v) was popped 2nd
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# 4. Therefore: a <= u
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# 5. We assume that u <= v and a <= b
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# 6. So we need to handle 2 cases of overlap, and one disjoint case
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# | u--v | u----v | u--v |
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# | a----b | a--b | a--b |
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u, v = intervals.pop()
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a, b = result[-1]
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if u <= b + 1:
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# Overlap cases
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result[-1] = (a, max(v, b))
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else:
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# Disjoint case
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result.append((u, v))
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return IntervalSet(result)
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def difference(self, other):
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"""Set difference for lists of intervals. That is, returns a list of
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intervals that bounds all values bounded by x that are not also bounded by
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y. x and y are expected to be in sorted order.
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For example difference([(1, 10)], [(2, 3), (9, 15)]) would
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return [(1, 1), (4, 8)], removing the values 2, 3, 9 and 10 from the
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interval.
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"""
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assert isinstance(other, type(self))
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x = self.intervals
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y = other.intervals
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if not y:
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return IntervalSet(x)
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x = list(map(list, x))
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i = 0
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j = 0
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result = []
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while i < len(x) and j < len(y):
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# Iterate in parallel over x and y. j stays pointing at the smallest
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# interval in the left hand side that could still overlap with some
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# element of x at index >= i.
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# Similarly, i is not incremented until we know that it does not
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# overlap with any element of y at index >= j.
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xl, xr = x[i]
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assert xl <= xr
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yl, yr = y[j]
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assert yl <= yr
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if yr < xl:
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# The interval at y[j] is strictly to the left of the interval at
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# x[i], so will not overlap with it or any later interval of x.
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j += 1
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elif yl > xr:
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# The interval at y[j] is strictly to the right of the interval at
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# x[i], so all of x[i] goes into the result as no further intervals
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# in y will intersect it.
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result.append(x[i])
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i += 1
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elif yl <= xl:
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if yr >= xr:
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# x[i] is contained entirely in y[j], so we just skip over it
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# without adding it to the result.
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i += 1
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else:
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# The beginning of x[i] is contained in y[j], so we update the
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# left endpoint of x[i] to remove this, and increment j as we
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# now have moved past it. Note that this is not added to the
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# result as is, as more intervals from y may intersect it so it
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# may need updating further.
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x[i][0] = yr + 1
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j += 1
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else:
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# yl > xl, so the left hand part of x[i] is not contained in y[j],
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# so there are some values we should add to the result.
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result.append((xl, yl - 1))
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if yr + 1 <= xr:
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# If y[j] finishes before x[i] does, there may be some values
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# in x[i] left that should go in the result (or they may be
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# removed by a later interval in y), so we update x[i] to
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# reflect that and increment j because it no longer overlaps
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# with any remaining element of x.
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x[i][0] = yr + 1
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j += 1
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else:
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# Every element of x[i] other than the initial part we have
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# already added is contained in y[j], so we move to the next
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# interval.
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i += 1
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# Any remaining intervals in x do not overlap with any of y, as if they did
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# we would not have incremented j to the end, so can be added to the result
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# as they are.
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result.extend(x[i:])
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return IntervalSet(map(tuple, result))
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def intersection(self, other):
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"""Set intersection for lists of intervals."""
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assert isinstance(other, type(self)), other
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intervals = []
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i = j = 0
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while i < len(self.intervals) and j < len(other.intervals):
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u, v = self.intervals[i]
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U, V = other.intervals[j]
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if u > V:
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j += 1
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elif U > v:
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i += 1
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else:
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intervals.append((max(u, U), min(v, V)))
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if v < V:
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i += 1
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else:
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j += 1
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return IntervalSet(intervals)
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def char_in_shrink_order(self, i: int) -> str:
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# We would like it so that, where possible, shrinking replaces
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# characters with simple ascii characters, so we rejig this
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# bit so that the smallest values are 0, 1, 2, ..., Z.
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#
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# Imagine that numbers are laid out as abc0yyyZ...
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# this rearranges them so that they are laid out as
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# 0yyyZcba..., which gives a better shrinking order.
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if i <= self._idx_of_Z:
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# We want to rewrite the integers [0, n] inclusive
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# to [zero_point, Z_point].
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n = self._idx_of_Z - self._idx_of_zero
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if i <= n:
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i += self._idx_of_zero
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else:
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# We want to rewrite the integers [n + 1, Z_point] to
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# [zero_point, 0] (reversing the order so that codepoints below
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# zero_point shrink upwards).
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i = self._idx_of_zero - (i - n)
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assert i < self._idx_of_zero
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assert 0 <= i <= self._idx_of_Z
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return chr(self[i])
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def index_from_char_in_shrink_order(self, c: str) -> int:
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"""
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Inverse of char_in_shrink_order.
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"""
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assert len(c) == 1
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i = self.index(ord(c))
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if i <= self._idx_of_Z:
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n = self._idx_of_Z - self._idx_of_zero
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# Rewrite [zero_point, Z_point] to [0, n].
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if self._idx_of_zero <= i <= self._idx_of_Z:
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i -= self._idx_of_zero
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assert 0 <= i <= n
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# Rewrite [zero_point, 0] to [n + 1, Z_point].
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else:
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i = self._idx_of_zero - i + n
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assert n + 1 <= i <= self._idx_of_Z
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assert 0 <= i <= self._idx_of_Z
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return i
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