100 lines
2.4 KiB
Python
100 lines
2.4 KiB
Python
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"""
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Some generic comparison utility functions.
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.. autosummary::
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:toctree: compare
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comparison
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observation
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"""
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def generic_cmp(value1, value2):
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"""
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Generic comparator of values which uses the builtin '<' and '>' operators.
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Assumes the values can be compared that way.
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:param value1: The first value
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:param value2: The second value
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:return: -1, 0, or 1 depending on whether value1 is less, equal, or greater
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than value2
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"""
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return -1 if value1 < value2 else 1 if value1 > value2 else 0
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def iter_lex_cmp(seq1, seq2, cmp):
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"""
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Generic lexicographical compare function, which works on two iterables and
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a comparator function.
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:param seq1: The first iterable
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:param seq2: The second iterable
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:param cmp: a two-arg callable comparator for values iterated over. It
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must behave analogously to this function, returning <0, 0, or >0 to
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express the ordering of the two values.
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:return: <0 if seq1 < seq2; >0 if seq1 > seq2; 0 if they're equal
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"""
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it1 = iter(seq1)
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it2 = iter(seq2)
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it1_exhausted = it2_exhausted = False
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while True:
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try:
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val1 = next(it1)
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except StopIteration:
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it1_exhausted = True
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try:
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val2 = next(it2)
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except StopIteration:
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it2_exhausted = True
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# same length, all elements equal
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if it1_exhausted and it2_exhausted:
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result = 0
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break
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# one is a prefix of the other; the shorter one is less
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elif it1_exhausted:
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result = -1
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break
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elif it2_exhausted:
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result = 1
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break
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# neither is exhausted; check values
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else:
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val_cmp = cmp(val1, val2)
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if val_cmp != 0:
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result = val_cmp
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break
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return result
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def iter_in(value, seq, cmp):
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"""
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A function behaving like the "in" Python operator, but which works with a
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a comparator function. This function checks whether the given value is
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contained in the given iterable.
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:param value: A value
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:param seq: An iterable
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:param cmp: A 2-arg comparator function which must return 0 if the args
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are equal
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:return: True if the value is found in the iterable, False if it is not
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"""
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result = False
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for seq_val in seq:
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if cmp(value, seq_val) == 0:
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result = True
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break
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return result
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