def lazy_lt(lseq, rseq):
"""Less-than comparison for two lazily generated sequences.
See ``lazy_lexicographic_ordering``.
"""
liter = lseq()
riter = rseq()
for left, right in zip_longest(liter, riter, fillvalue=done):
if (left is done) or (right is done):
return left is done # left was shorter than right
sequence = callable(left)
equal = lazy_eq(left, right) if sequence else left == right
if equal:
continue
if sequence:
return lazy_lt(left, right)
if left is None:
return True
if right is None:
return False
return left < right
return False # if equal, return False
def lazy_eq(lseq, rseq):
"""Equality comparison for two lazily generated sequences.
See ``lazy_lexicographic_ordering``.
"""
liter = lseq() # call generators
riter = rseq()
# zip_longest is implemented in native code, so use it for speed.
# use zip_longest instead of zip because it allows us to tell
# which iterator was longer.
for left, right in zip_longest(liter, riter, fillvalue=done):
if (left is done) or (right is done):
return False
# recursively enumerate any generators, otherwise compare
equal = lazy_eq(left, right) if callable(left) else left == right
if not equal:
return False
return True