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